Guest post by Alec Rawls
Beneficial climate change allowed modern humans to emigrate out of Africa and spread around the globe says the new PBS documentary “First Peoples,” but it fails to mention that the era it designates as “good times” was several degrees warmer than today.
A critical moment in human history is intoned with intense drama (21:08-21:52 here):
The movement of prehistoric people was affected by the climate, which fluctuated over thousands of years.
I turned up the volume, knowing that if there was anything a warming alarm-dog could find to bark about, it was about to be featured front and center.
In bad times the Sahara was an un-crossable barrier, but in good times, when the climate was wet, the desert disappeared. Any adaption that emerged in one part of Africa could spread to other parts of the continent….
On screen an outer-space view of North Africa and the land bridge to Asia and Europe changed from arid to green (top image), then the segment ended.
“That would have been a warm period,” I said to the television
Not just because the PBS warming-alarm-dog would have barked if it was the bad/dry period that was warmer, but because a warmer planet, with more evaporation and more rain, should on average be wetter. Then there is the known effect that the most recent period of global warming had on North Africa, seen in the greening of the Sahel between 1982 and 2003:
It was the Eemian
A quick search for “wet Sahara” and modern human migration turns up this from Popular Archeology magazine:
Study Confirms Ancient River Systems in Sahara 100,000 Years Ago
Evidence from past research has suggested that, sometime during the period between 130,000 and 100,000 years ago, the Sahara desert region we know today was wetter, featuring rivers and lakes, providing an environment that many scientists theorize permitted the earliest modern humans to migrate northward from points southward in Africa toward the Mediterranean coastline and areas eastward into the Levant.
And something on Eemian temperature history:
Greenland ice cores reveal warm climate of the past
The new results show that during the Eemian period 130,000 to 115,000 thousand years ago the climate in Greenland was around 8 degrees C warmer than today.
Thou shalt provide no ammunition to climate deniers
Like the dog that didn’t bark in Conan Doyle’s Silver Blaze, a warming-alarm-dog will never bark at its master, or its paymaster. There is a lot of funding available for academic experts on climate-driven human migrations. So says the primary climate change funding guide. From AR5, WGII, Summary for Policymakers, page 11:
Uncertainties about future vulnerability, exposure, and responses of interlinked human and natural systems are large (high confidence). This motivates exploration of a wide range of socioeconomic futures in assessments of risks.
But that funding is only available to those who toe the “consensus” line that human activity is causing dangerous amounts of global warming. Telling the world that mankind’s big climate break came when global temperatures were several degrees higher than today would needlessly put a paleoanthropologist’s academic and television career at risk.
Much wiser to just leave that inconvenient truth out, and who wants to give ammunition to those nasty science deniers anyway? They’ll just spread the truth to even more people.
Bonus dog that didn’t bark
The research paper reported in Popular Archeology magazine (confirming ancient river systems in Sahara 100,000 Years Ago), is a hydrological modeling study, driven first and foremost by the temperatures that prevailed in the era under study, so the five authors know in great detail that they are modeling a substantially warmer period than today, yet the full published study never mentions this key fact. The closest they come to mentioning that the Eemian was warmer than today is this hint from the first paragraph of their “Discussion” section:
This reconstruction is highly compatible with evidence of widespread palaeosols deposited on the margins of this system during the less pronounced Holocene humid period [22].
Okay, so they are admitting that the Holocene is humid. Everyone knows that the Holocene is an interglacial so they are kinda-sorta admitting that warm is humid, at least in North Africa, and they tell us that the Eemian was more humid, so they are hinting that the Eemian was warmer than today, only they just can’t bring themselves to actually say that it was warmer, even though this is the key explanatory variable in their wet-Sahara theory.
The authors say they did not get any funding for this research. Either they are trying really hard to change that or they are ideologically self-driven not to speak any inconvenient scientific truths that “science deniers” could propagate. Only anti-deniers can be counted on to keep the truth suppressed.
There you go using rational processes and critical thinking again. The climate obsessed community bans those pesky things.
The skeletal remains of “Lucy”, apparently what we (humans) evolved from, was found in what is now northern Kenya (?). Her “remains” are still in what is now Ethiopia. I have pictures of the remains. The view is that climate change forced “tree dwellers” to walk on land and in grasses…eventually walking up-right!
Beneficial climate change allowed modern humans to emigrate out of Africa and spread around the globe says the new PBS documentary “First Peoples,” but it fails to mention that the era it designates as “good times” was several degrees warmer than today.
Actually the first ‘out of Africa’ migration occurred ~70,000 years ago at a time of low temperatures and low sea levels (ultimately arriving in Australia).
On screen an outer-space view of North Africa and the land bridge to Asia and Europe changed from arid to green (top image), then the segment ended.
“That would have been a warm period,” I said to the television
Except that the land bridges expanded when the temperature was lower.
This particular land bridge (Middle East) was always there, as human history is concerned.
So what about those Eemian Homo sapiens at Skhul and Qafzeh?
For that matter H. Ergater’s descendants, esp. H. Erectus made it out of Africa long, long before that. But much of Europe was not populated as recently as 40,000 years ago.
New book published by the British Museum of Natural History records several migrations to the British Isles to 1 million years BP
Lucy was Australopithecus and lived ~3.2 Mya, not sure how relevant that is to the last 70,000 years?
We are only 2 million years into the current 12 million year ice age, so Lucy was under a regime different from now. I believe that regime was consistently warmer than now, and there might even have been no icecaps at her time.
higley7
July 6, 2015 at 9:26 am
Yes. Lucy lived in the late Pliocene, when the world was warmer, but still cooler than during the Miocene, and with wooded areas separated by grassland due to drier conditions.
Australopithecines evolved into genus Homo shortly after the onset of the Pleistocene glaciations, as tropical Africa got even drier.
(Australopithecus and Homo probably don’t merit separate generic names. Indeed even Pan and Homo likely wouldn’t be considered different genera if we weren’t dealing with humans, as Linnaeus himself observed.)
Patrick July 6, 2015 at 5:07 am
“…The view is that climate change forced “tree dwellers” to walk on land and in grasses…eventually walking up-right!”
Perhaps, but it might also be just better by giving our ancestors many more opportunities, so that we just started walking because that was what’s next. I think nature is fundamentally opportunistic so it doesn’t always need obvious stimulus to make a change.
Also “walking upright” reduced exposure to sun and heat?
Stephen: If the mutation does not provide an advantage, it won’t be selected for.
Patrick: If that were a major factor, I would expect to see other animals evolving towards a vertical posture.
Right on about Lucy . Footprints in mud are not made on dry parched land.
I wish I could post pictures, I have them from the museum in Addid Ababa.
Do you have access to a scanner?
You need to reverse the position of the pictures to get the Led Zep mojo going.
Immigrant Song?
Good Times, Bad Times, you know I had my share
It is generally acknowledged that the previous interglacial, the Eemian, was warmer than today. Even the IPCC admits that in its Arctic Impact Assessment Report (2005)
Paragraph 2.7.3.1
According to most proxy data ,the last interglacial was slightly warmer everywhere than at present (IPCC, 2001c). Brigham-Grette and Hopkins (1995) reported that during the Eemian the winter sea-ice limit in Bering Strait was at least 800 km farther north than today, and that during some summers the Arctic Ocean may have been icefree. The northern treeline was more than 600 km farther north
And from Wikipedia
At the peak of the Eemian, the climate was much hotter than today
Sea level at peak was probably 4 to 6m (13 to 20 feet) higher than today
So, let’s take it that the previous interglacial was indeed warmer, although CO2 levels were much lower (about 280ppm).
You are almost there MikeB, just need to state that it was warmer AND more beneficial at the same time.
Personally I attribute the greening of the Sahel to increased CO_2 as much as to increased humidity if not more so. Increased CO_2 causes a decrease in the pore size of many plants (they can get with they need via smaller stoma and do) which increases their drought resistance. Plants can get by with less water because they respire less to get the CO_2 they need. Humans do the same thing, which is why people with compromised respiration often wheel little oxygen tanks around with them. In pure O_2, you need to breathe less (and in fact, NEED to breathe less).
It isn’t just the Sahel. My back yard is “greening” — growing more for any given exposure to rain etc. Trees, grass, flowers, everything is lush.
rgb
Yes, obviously only anecdotal, but we had a dry May, and my grass (and weeds) stayed green. Never watered once. Still have not and it’s continued dryer than usual.
Well, the Pope may be coming to US so I am sorry that with all the lovely CO2 here in Northern Vermont (power plant converted to burning wood chips = 150% improvement in CO2 emissions over former coal burning) I must fight the “harmony” of Mother Nature knocking back weeds in the vegetable garden and cutting the grass every week while ducking through the heavy boughed and ripening apple trees on my lawn tractor.
Increased CO2, more efficient water and nitrogen use through stomata for abundant biosphere – what’s not to like?
How many acres of forest need to be burned to keep up with the replaced coal fired plant? Just asking, of course in developing countries the wood is usually converted first to charcoal to simplify distribution and make it possible to use as for cooking. Creates a heck of a mess if the township is near a city with a thermal inversion.
Careful, CO2 is much higher today than than the Emian. This is actually the one compelling argument that the atmospheric increase is substantially human.
gymnosperm:
You say
Ice core data agrees with you but stomata data does not.
And rgbatduke was talking about stomata data.
Richard
I agree that the stomata data should rule where the stomata “breathed”. I have not seen stomata data approaching 400 ppm.
Richard,
The highest stomata data I’ve seen for the Eemian imply at most around 330 ppm. I must have missed the stomata studies you’ve found for 400 ppm or more during the Eemian. Would greatly appreciate links to them.
Thanks.
Sturgishhooper:
I asserted that ice core data agrees with “CO2 is much higher today than the Emian” but stomata data does not and you then reasonably requested
I freely admit that I cannot “provide links to them” but I stand by my assertion. I explain this intransigence – with links to supporting papers – as follows.
The Eemian began about 125,000 years ago. Hence, samples of plant material for stomata analyses are sparse for the Eemian, and almost all arguments concerning stomata data of Eemian atmospheric CO2 concentration derive from the work of Rundgren et al. (2005) who studied specimens from the Hollerup sediment core .
I suspect your comment refers to their Figure 7 which shows the CO2 reconstruction based on Betula and Quercus leaves with CO2 levels typically between 240 – 330 ppmv and typically ±15 ppmv. This finding is comparable to the range of Eemian CO2 indicated by the Vostok ice core record.
This finding of Rundgren et al. is widely cited. For example, van Wirdum (2012) cites it in his MSc thesis
van Wirdum accepts the Rundgren et al. results as being correct and very reasonably concludes from that
However, this coincidence of stomata and ice core data is atypical. Many other studies show stomata data indicate much higher atmospheric CO2 than ice core data for the same times. Indeed, it is strange that Rundgren et al. find such a correspondence but do not explain why this atypical correspondence exists.
Although Woodward (1987) provided the seminal work on stomata as CO2 indicators, the works of Wagner in this field are of especial note. I here cite as example Wagner et al. (2004) which reports values of atmospheric CO2 concentration of 400 ppmv indicated by stomata data when ice core data indicates ~280 ppmv.
And I note that this paper concludes
So, although I cite and link to the stomata data of Rundgren et al. (2005) which supports the statement in your question, I stand by my assertion which disputes that statement because the coincidence of stomata data and ice core data reported by Rundgren et al. (2005) is atypical and within my knowledge it is unique.
I hope this answer is sufficient but, if not, then I would welcome your response.
Richard
Richard,
I know, you prefer the stomata proxy data above the ice core direct (smoothed) CO2 measurements… If you don’t like the data, like in the case of the Eemian, even the stomata data must be wrong…
Even if there was some migration of CO2 in the ice cores, all what that does is that the resolution broadens, that means that the real averaging gets 22 years i.s.o. 20 years as is the case for the theoretical migration of CO2 in relative warm (-23°C), coastal ice cores like Siple Dome at middle depth and 40 years at full depth.
More inland ice cores like Vostok which spans 420,000 years don’t have that problem, as these are much colder (-40°C). The main problem in this case is to synchronize the average gas data from the ice cores with the dating of the leave fragments in the NH sediments.
The differences between the two CO2 reconstructions for the Eemian are:
– Stomata data: resolution +/- 200 years, accuracy between +/- 20 ppmv and +/- 30 ppmv
– Ice core data: Vostok: +/- 600 years, accuracy +/- 2 ppmv
While the ice core have a worse resolution, there is no reason that – even with migration – the average does change over time: migration – as far as it happens – does change the resolution, but that doesn’t change the average over the period of resolution.
On the other hand, stomata data are a proxy, where the influence of local CO2 levels (not “background”) on stomata density needs to be calibrated against direct measurements and ice cores over the past century. The main problem is that there is no possibility to know how the local bias changed in previous millennia due to landscape changes, climate, main wind direction, etc… The only possibility is to recalibrate them again against ice cores for the overlapping periods.
Thus anyway, if there is a discrepancy between ice cores CO2 and stomata CO2 over the full period of resolution of the ice cores, the ice cores are right and the stomata data are wrong…
“if there is a discrepancy between ice cores CO2 and stomata CO2 over the full period of resolution of the ice cores, the ice cores are right and the stomata data are wrong…”
Why?
Ferdinand:
No! You do NOT “know {I} prefer the stomata proxy data above the ice core direct (smoothed) CO2 measurements…” because I don’t. I consider both to provide useful but different indications which all require interpretation.
And the ice core data are NOT “direct measurements”. Direct measurements are not “smoothed” and would not provide an ice age to gas age difference.
Please read what I wrote because I say I do NOT agree the stomata data of Rundgren et al. (2005) and I explain why. I wrote to sturgishooper
I am rejecting the stomata analysis of Rundgren et al. (2005) because it uniquely fails to provide higher than ice core values of paleo atmospheric CO2. Indeed, the reason you refuse to accept ALL stomata data is because typical stomata data provides higher indications of paleo atmospheric CO2 than ice cores.
Richard
Richard and Ferdinand,
Thanks for the detailed responses.
Comparison of data from different sources is important in paleoclimatology. Both ice cores and stomata, as well as other observations and proxies, of course have problems.
If stomata do indeed, as Richard is convinced, systematically show higher ancient CO2 levels than ice, then I would be inclined to accept his statement, since IMO the farther back you go in ice, the greater the uncertainty.
If the Eemian can be shown to have enjoyed CO2 concentrations as high as today’s, then some significant questions can be answered, generally not in ways the IPCC would like.
Richard,
CO2 measurement methods (NDIR, GC, mass spectrometer) in ice cores are exactly the same as for CO2 measurements in open air or firn. That are direct measurements. Not momentary or from one year but averaged over several (less than a decade for Law Dome) to many years (600 for Vostok and 560 for Dome C). Neither are stomata index data: that are not direct measurements at all and neither of one year: a few years over the last century up to 200 years for the Eemian period.
The ice age – gas age difference is not of the slightest interest for the accuracy of the CO2 data: even if there are thousands of years of difference, but the ice pores were wide enough and the bubble closing was fast enough, the ice core bubbles would show the same CO2 levels as in the above atmosphere, whatever the age of the surrounding ice. All what matters for the resolution is the snow accumulation rate and its effect on pore diameter (= speed of diffusion) and the time needed to fully close all air bubbles.
What you still refuse to admit is that the smoothing of the CO2 levels in ice cores doesn’t change the average over the resolution period. That is the main difference between ice cores CO2 and stomata CO2 data: the ice cores don’t reflect all details of fast changes, but they accurately reflect the average CO2 levels over the period of resolution, which the stomata data only approximate.
I am rejecting the stomata analysis of Rundgren et al. (2005) because it uniquely fails to provide higher than ice core values of paleo atmospheric CO2
Richard, there is no reason at all that the stomata data must show higher values than the ice cores, or they simply are bad proxies. Stomata (index) data are calibrated against direct measurements and ice core data over the previous century. That is 40 years of direct measurements (1960-2000) and 60 years of ice core CO2 data (1900-1960). If they fail to show the same average historical CO2 levels over the resolution period of the ice cores in the far past, then the local/regional bias of the stomata proxy changed over time and they need recalibration with the ice cores CO2.
Sturgishooper,
If stomata do indeed, as Richard is convinced, systematically show higher ancient CO2 levels than ice, then I would be inclined to accept his statement
As said to Richard, there is no reason at all to expect that stomata data are by definition higher than ice core CO2 data, as the stomata (index) data are calibrated against ice cores over the past century.
Stomata by definition are from leaves of land plants. These grow in CO2 conditions which change from hour to hour and season to season.
From Tom van Hoof (stomata specialist) I have heard that the stomata (index) reflects the average local CO2 level of the place where the trees/plants grow over the previous growing season. For a typical semi-rural place (Giessen, mid-West Germany) that gives following monthly averages:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/giessen_mlo_monthly.jpg
Compared to Mauna Loa or the South Pole, which are real background, there is already a bias of about +40 ppmv, for which is compensated by comparing the stomata index data with ice cores.
The main problem is that you don’t know how the local bias changed over time, due to landscape (and land use) changes in the main wind direction, even the main wind direction may have changed in certain periods like during the Little Ice Age…
Ferdinand, Greenland and Antarctica are hardly the ideal places to measure CO2. True, it mixes exceptionally well, but on a Carbon Starved Planet (your words which I wish permission to borrow), living things will hijack every Carbon atom they can get their “hands” on. This hijacking will take place in the tropics and the temperate forests
Ferdinand Engelbeen:
You wrongly – and repeatedly – assert
It is an empirical fact that stomata data DO provide higher values than ice core data.
In this sub-thread I explained – with reference link and quote – that typically stomata data provide higher values than stomata data. Indeed, the reason I dispute the stomata data of Rundgren (2005) is because they atypically provide data that agrees with the ice core data.
And the reason you persistently denigrate stomata data is because they typically provide data that is higher than ice core data.
Richard
Sorry for a typo.
I wrote
“In this sub-thread I explained – with reference link and quote – that typically stomata data provide higher values than stomata data.”
but I had intended to write
“In this sub-thread I explained – with reference link and quote – that typically stomata data provide higher values than ice core data.”
I think the error is obvious, but I write to correct it and to apologise for it.
Richard
Richard,
If stomata data are derived (not the same as measured) from plants which by definition grow near ground on land which by observation have higher CO2 levels than in the bulk (95%) of the atmosphere, then you need to calibrate the stomata data against other, more reliable, measurements. Which are direct measurements at the South Pole and Mauna Loa since 1960 and ice core CO2 data over the past 800,000 years.
If even stomata specialists use ice core data to calibrate their stomata data, that implies that the ice core data are more accurate than the stomata data. The main advantage of stomata data is that they have a better resolution for the same periods back in time, but the absolute CO2 values and the variability of the stomata data is based on local CO2 levels, which may have changed their local bias over the centuries/millennia of the past.
Moreover, there are several CO2 reconstructions which show similar CO2 levels as in ice cores:
http://www.geocraft.com/WVFossils/Reference_Docs/Late_Holocene_CO2_3000-4300_BP_Jessen_etal_2005.pdf
See Fig. 6.
The repeatability of the SI measurements for the same age is +/- 25 ppmv and the authors warn:
All SI CO2 reconstructions tend to have large error margins and a running average is usually calculated to illustrate the trends. In addition, some species, including Betula pubescens and B. pendula appear to reconstruct CO2 at fairly consistently elevated concentrations (often ca. 30 ppmv) relative to Antarctic ice core data, so quantification of stomata based CO2 data is clearly still associated with some problems.
You see why I prefer the original (ice core CO2 data) before the surrogate (stomata CO2 proxy data).
gymnosperm:
Ferdinand, Greenland and Antarctica are hardly the ideal places to measure CO2. True, it mixes exceptionally well, but on a Carbon Starved Planet (your words which I wish permission to borrow), living things will hijack every Carbon atom they can get their “hands” on.
In fact no problem: on long term (over the past few million years) the oceans were the dominant CO2 providers/removers, as can be seen in the parallel CO2 and 13C/12C changes over ice ages and interglacials. Plant expansion under warmer conditions and reverse was of lesser influence.
It seems that current plant CO2 uptake and decay is more or less in equilibrium, with only 1 GtC/year (~0.5 ppmv/year) more uptake than release under the current increased CO2 pressure in the atmosphere…
Ferdinand,
Out of one side of our mouths we say that half of human emissions (4-5 GtC) are being absorbed and out of the other side we say that plants and the ocean are only only a GtC each out of balance. Where is the other 2-3 GtC going?
gymnosperm,
The rest is absorbed by the oceans. Current estimates are approximately:
– 9 GtC/year human emissions
– 1 GtC/year uptake in the biosphere
– 0.5 GtC/year uptake in the ocean surface layer
– 3 GtC/year uptake in the deep oceans
– 4.5 GtC/year increase in the atmosphere
The 1 GtC/year in the biosphere is the net exchange (based on the oxygen balance). As humans (still) clear a lot of (tropical) forests, the real uptake by the plants may be around 3 GtC/year where forest clearing gives an extra 2 GtC/year CO2 emissions above fossil fuel use. But the land clearing figures are far more uncertain than fossil fuel use, which are based on sales (taxes…) and burning efficiency…
Thanks Ferdinand,
I have been working on an isotope integrated Carbon cycle. It was impossible to balance because the atmosphere goes negative PDB way too fast. I realized last week that the key might be the +-4.5 human absorption which if true requires far more asymmetry between the atmosphere and sinks than the best models show. Sure enough, when I skew the biosphere cycle by 5 Gt (115 out to biosphere, 110 back to atmosphere) it balances. Ocean imbalances will not do the trick as they yield only +2/Gt as opposed to +18 for the biosphere.
Gymnosperm,
Oceans are not only helping with their unbalance: the deep ocean exchanges, even in balance do help a lot as that is 40 GtC going in and out (or to be more realistic: 38.5 GtC/year in, 41.5 GtC/year out). The overall 13C/12C level of these 40 GtC is about -6.4 per mil over the past Holocene. That is a lot of “thinning” of the human “fingerprint”…
The difference in source/sink from the biosphere is only ~1 GtC/year for the 13C/12C balance: what is cleared as forests has about the same isotopic composition as what is taken away, thus the net contribution is equivalent to ~1 GtC at about +24 per mil left in the atmosphere due to the preferential removal of 12CO2.
Ferdinand,
The human fingerprint is even further thinned by the 60 GtC from soils at about -21. I do not believe the net effect from vegetation is as high as +24 because C4 and CAM plants evolved since the Pliocene to need less CO2 (and water). Factoring in their prevalence I get +18 net but this is uncertain.
How do you derive -6.4 for the oceans? My information is +2 in and -10 out for a net of -8.
rgbatduke,
I hesitate to contradict you here, since I greatly admire your contributions to WUWT, but I consider water a more significant variable than CO2 in this context.
Plant respiration is not the same as animal respiration in everyday language; it is the chemical process of oxidation of glucose within cells and results in release of CO2, not absorption as in photosynthesis.
The plural of stoma is stomata. There’s a difference between ‘increased CO2’ and ‘high CO2’.
Your backyard observations of greening more for any given exposure to rain rather fly in the face of Liebig’s law of the minimum.
IMO the Sahel hasn’t gotten much more rain if any than during the period of concern over desertification thirty or more years ago. The variable that has changed and IMO led to its spread into formerly desert regions in recent decades is CO2 concentration.
I’ve noticed that plants leave their stomata open now for less time than they used to. I have to spray weeds ever earlier in the morning to have maximum effect, ie while they’re still gasping in CO2. And my lawn stays greener longer with less water than before.
In Physiological plant ecology: ecophysiology and stress physiology of funcional groups (Springer, 2003), Walter Larcher writes:
According to over 3000 scientific publications on the biology of CO2 effects, a broad spectrum of growth responses to CO2 enrichment exists. Since elevated CO2 often reduces the plants’ demands for other resources, CO2 effects on growth do not simply follow Liebig’s law of the minimum. Plants exposed to elevated CO2 need less enzymes (and thus lower quantities of leaf proteins and nitrogen), lose less water (can cope with less soil moisture and often operate at smaller stomata openings) and need less light (because of a shift in the light compensation point for photosynthesis) to reach the equivalent, or even higher photosynthetic rates than plants growing under control conditions with “normal” CO2 concentrations.
sorry, full weblog reference: re Sylvan Wittwer work in plant physiology
https://buythetruth.wordpress.com/2009/08/15/co2-enrichment-and-plant-nutrition/
I bet you can’t find 3,000 publications that say CO2 turns brown areas green. Water does that.
CO2 makes green stuff bigger.
Mebbe,
The earth is greening, especially in warm and dry areas of the earth, as recently shown by satellites which are specifically equipped for detecting chlorophyll:
http://onlinelibrary.wiley.com/doi/10.1002/grl.50563/full
Yes, Scientific American called anthropogenic CO2 “the precious air fertilizer,” back when their editorial standards were higher, and that was even before the beneficial effects of CO2 on plant stomata density and drought resistance were known.
I’m just referring to a number (a lot less than 3000, but it wouldn’t surprise me if there were 1000s and plant growth is a critical pathway of human existence all over the world) of papers I’ve read on greenhouse studies of increased CO_2. And no, there isn’t any difference between increased and high — if it is confusing to you, let’s simply refer to ppm. At 300 ppm plants grow at one rate, consume water and other resources at one rate. At 400 ppm plants (depending on their leaf type) grow roughly 10-15% faster and larger with the otherwise same resources, and if they are resource constrained — in particular if they are grown in partial drought conditions — they are much more tolerant of the drought. As pointed out below/above, this appears to be because the plants conserve moisture better by respiring less as well as because the increased CO_2 alters enzymatic pathways.
It (apparently) isn’t simply a matter of the law of the minimum because plants are not perfectly or uniformly efficient in their use of water and increased CO_2 alters their practical efficiency.
In any event, I’m not trying to explain something I’ve barely studied — I had a single biology class back in 9th grade in high school and that is it — but I’m reporting empirical results from the literature. Whether it is an explanation like the one above or black magic, it is an empirically verified fact that plants grow more on the same resources if CO_2 is raised, and that the benefits continue beyond 300->400 on up. If I recall correctly, the recommended CO_2 levels in professional greenhouses is around 1000 ppm — 0.1% CO_2, 2.5x the current atmospheric level. I’m guessing that at some point the benefit saturates and the law of the minimum kicks in, but obviously it is well beyond 400 ppm.
You can shop for this stuff online:
https://www.1000bulbs.com/product/92576/GROW-APCECOTH.html
This isn’t rocket science, in other words — it is old technology and well-known facts.
rgb
RGB,
The benefit maxes out around 1300 ppm, ie the upper end of CO2 levels maintained in real greenhouses.
rgbatduke,
Yes, I think we all know that CO2 is essential to plant growth and that, in general, enhanced CO2 means enhanced growth; your original assertion was that you could detect the signature of an annual rise of 2ppm of CO2 in the plants in your back yard and confidently say that water availability did not account for the “greening”.
You didn’t indicate the time period of your observations. If it was from two years ago to last year, then that suggests an unbelievable (literally) sensitivity. If it was from 30 years ago to last year, then that shows a remarkable memory. If it was averaged over 30 years, I assume you kept some serious records.
Your link to a hydroponics store is an all-in-one controller for a four light basement garden for the plug and play crowd that have a shed full of Carb-Boost and Kabloom, but I guess it does make your point that the technology exists, which you think I didn’t know.
I assume you mean the modern greening of the Sahel? Because the greening of the Sahel during the Holocene Climate Optimum likely occurred on account of overall expansion of the African Rain Belt.
http://www.nature.com/ngeo/journal/v4/n1/full/ngeo1039.html
The size of stomata isn’t variable: it’s the density, or the number of stomata per unit area, that varies.
~~~~~~~~~~~~~~~~~~~
Yet, in theory the same result due to having more stomata could be attained by simply having bigger stomata with no difference in stomata number – however, plants vary stomata number and not stomata size.
http://www.esa.org/tiee/vol/v1/experiments/stomata/stomata_description.html
~~~~~~~~~~~~~~~~~~~
rgb says:
rgb, I’d agree — when the sun is closest in the NH summer (10kya), the Sahara “greens” because the monsoon expands over much of it. When the sun is farthest in NH summer — a desert. So there isn’t a solar-precession reason for the current greening — just the opposite.
Or they were simply trying to prevent rejection because they wrote a ‘denialist’ article.
The Sahara was also much wetter with lakes and rivers during the warmer Holocene Optimum from 9,500 years ago to 4,000 years ago.
And before 8 million years ago, the last time the general Earth climate was warmer, the Sahara was completely forested and so was the rest of the land surface.
Yes, and human ancestors evolved in response to the drying world, as East and South African apes needed to walk from isolated wood to wood.
Is that an ultrasound of somebody’s liver before and after climate change?
I come from an area with the highest concentration of CO2 anywhere in Europe, although there is no any industry worth mentioning (all geological origin – tectonics). Every time I go back I am surprised how the nearby rocky hillside has been more and more taken over by bushes of the wild uncultivated pomegranates (species prosper in arid warm areas).
http://www.vukcevic.talktalk.net/SEE-CO2.jpg
I have never seen (in 20+ years) a greener spring (and a greener summer) than this year in South Colorado. The vegetation is almost tropically triumphant after long years of drought. It’s rains, of course, but also CO2. And it’s a bit cooler than usual.
“…..Those real world observations
Are a threat to us all,
Like those dreadful ‘deniers’
Who monitor the temperature fall.
Mother Nature mustn’t be allowed
To get in the way,
She needs to understand
Man has the ultimate say.”
http://rhymeafterrhyme.net/real-world-observations-a-threat-to-us-all/
I read the Voyage of the Argo by Apollonius of Rhodes recently. The last part involves the Argo being stranded in the shallow sea of North Africa.
It’s not just the Nile Delta – the poem talks of a shallow, marshy sea south of the Mediterranean.
It was believable only 2500 years ago.
Lake Chad was once the largest fresh water lake in the world. It’s dust now fertilizes the Amazon
Then of course there is the taboo subject of how the immigrants from mother Africa started to differentiate or shall we say adapt into different appearances, with various skin pigments and other characteristics like diverging skeletal structures. Ok, anyone care to touch or trample on that controversial subject ? Weather driven adaptation perhaps ?
IMO it’s not all that controversial, since DNA from tens of thousands of years ago has been recovered.
At present, it appears that the first Moderns to enter Europe were darker complected, although not West African in physiognomy, as shown on UK TV. Neanderthals of course were lighter complected, after so long in a less sunny clime, hence adapted to produce more vitamin in their skin thanks to less melanin.
The moderns also got progressively lighter skin during their stay in northern climes from c. 50 to 10 Ka.
The invaders from the Middle East around 8000 years ago brought even lighter complexions with them along with agriculture and probably Indo-European languages. They did not completely swamp out the Paleolithic European genome, however.
That controversial subject trampled here.
Also google Prof Leonard Jeffries.
That is the biggest load of shit I have ever read,
Wizzum,
With the possible exception of the latest “pile of filth” from the IPeCaC.
Amazingly, they also managed not to mention the trumpeting elephant that CO2 levels were apparently much lower (around 280 ppm) then meaning, gasp, that something else caused temperatures to surpass current warming by several degrees. The bonus elephant being that today, we have the best of both worlds; a period of relative warmth (not quite equal to the MWP, but we’ll take it) in addition to an increase in CO2, which is in large part responsible for a greening planet.
PBS promotes new ideas with pride, even though a majority of them are flawed ideas spun in a non fact check media world with undertones of agenda and diversion from science process.
I don’t know to which migration out of Africa the PBS referred. There have been many.
H. ergaster/erectus left Africa (or evolved in Eurasia) about two million years ago, perhaps via the Saharan pump.
Doesn’t matter really. Unless you have boats (which no species before H. sapiens had), getting out of Africa is only possible when the Sinai/Negev desert is passable, i. e. during warm (and wet) interglacials.
By the way Sinai/Negev, though not a very large desert, is actually one of the driest and most desolate deserts on Earth.
tty,
“Unless you have boats (which no species before H. sapiens had)”
You may very well be right about purposeful migration and voyaging.
Some dispersal, however, may have involved ‘chance’ crossing of water – there is an ‘island, floating’ in Lake Victoria – per the BBC News – at least, a few days ago they published: –
http://www.bbc.co.uk/news/world-africa-33226626
Now – the transfer of a v i a b l e population would have been uncommon.
Uncommon – certainly.
But not, I suggest, impossible.
It may not have happened. Or not.
However.
That plu-perfect paragon of definitive sites, Wikipedia [which even I can edit] has, under Homo erectus [link – https://en.wikipedia.org/wiki/Homo_erectus ] – downloaded at about 2004 Z, 6 July 2015: –
QUOTE
Use of tools
Homo ergaster used more diverse and sophisticated stone tools than its predecessors. H. erectus, however, used comparatively primitive tools. This is possibly because H. ergaster first used tools of Oldowan technology and later progressed to the Acheulean while the use of Acheulean tools began ca. 1.8 million years ago, the line of H. erectus diverged some 200,000 years before the general innovation of Acheulean technology. Thus the Asian migratory descendants of H. ergaster made no use of any Acheulean technology.
In addition, it has been suggested that H. erectus may have been the first hominid to use rafts to travel over oceans.
The oldest recorded stone tool ever to be found in Turkey reveals that humans passed through the gateway from Asia to Europe much earlier than previously thought, approximately 1.2 million years ago.
END QUOTE
[I have deleted the reference hyperlinks, and highlighted by ‘Return’ the sentence about rafts ]
Now, rafts are not boats – but rafts will [with good luck, good currents and good weather] – sometimes – get you to a new place, perhaps with the family, and the family’s fire.
Perhaps.
If you don’t capsize them first!
But with many tens of thousands of years [or maybe hundreds of thousand of years] there may have been many chances – only a very few of which ‘needed’ to be successful . . . . . .
Of course, in a Cold [low sea level] period the Bab el-Mandeb Strait may have been [comparatively] easily crossable – depending on the driver. Famine, tribal trouble, major fires . . . . We can speculate. It is possible we may never know!
Auto
A seafarer, who believes it possible that seafaring [if not purposeful seafaring, necessarily] may antedate his own species.
I agree that all the migrations by genus Homo out of Africa probably occurred during wet intervals, but it’s not impossible to have happened under conditions similar to the present.
The Wadi al-Arish (possibly the biblical “Brook of Egypt”) for instance carries away the flow of flash floods, and there are oases around permanent springs in the Sinai. Al-Arish gets over an inch of rain in January and more than 8/10 in December.
Science doesn’t know whether erectus- or heidelbergensis-grade humans rode floating logs and mats or not, whether accidentally or on purpose. H. floresiensis, “the Hobbit” lived on Flores Island, which even during the LGM was still an island.
New World Monkeys appear to have gotten to South America from Africa tens of millions of years ago, when the Atlantic was smaller, but still a formidable barrier, even assuming islands.
PS:
The ancestors of Asian elephants and mammoths managed to migrate out of Africa in the late Pliocene, around three million years ago.
Of course elephants are good swimmers, so need not necessarily have crossed the Sinai.
Forget the climate change aspect of this. If the migration out of Africa happened in this time frame did we migrate as one race or were we already multiple races? A little over 100,000 years seems a little short on time to explain the different races we have. Am I missing the boat here?
Humanity doesn’t have any races in the biological sense of the term, ie subspecies. However the different appearances of groups from various parts of the world are surprisingly recent.
The modern East Asian physiognomy probably arose during the 8200 BP cold event, for instance. But other traits of this geographic population are more ancient, such as tooth structure.
The ancestral modern human skin color is probably the reddish tone of the Khoi San people (Bushmen), followed by darker deeper in tropical Africa, then lighter during the spread out into Eurasia.
Mongoloid, Negroid, and Caucasoid. 3 racial groups. You never hear the first 2 mentioned. Caucasoid has turned incorrectly into caucasian which refers to someone from the caucasus. The new definition of the term is used to identify someone as white. Caucasoid however includes skin tones ranging from white to black. The mainstream refers to Asian and black and Caucasian as race. This is incorrect.
“Am I missing the boat here?”
The story is nowhere near that simple. Right now there seem to have been two significant pulses out of Africa ca 70kya and 100kya plus all kinds of surges back and forth in Eurasia (much of it driven by climate). The science is still sketchy but it seems that each new discovery adds complexity.
If you are curious, the blogging of Razib Khan and John Hawks would provide a good starting point, but you are not going to find a simple solid story.
For modern Homo sapiens, yes, but there were also migrations to and fro by earlier species or grades of our genus.
As for H. sapiens sapiens, our modern subspecies for instance surged back and forth in the Levant, displacing Neanderthals when it was warmer and retreating when colder, leaving the caves to our bulkier cousins at those times.
The period during the last glaciation for this subspecies see-saw was roughly 90 to 60 Ka.
Homo heidelbergensis probably left Africa around 650,000 years ago and evolved into Neanderthals in Eurasia about 300,000 years ago. Home sapiens [us] evolved from the African population of heidelbergensis about 200,000 years ago. Modern humans had a go at leaving Africa about 125,000 years ago but retreated back to Africa. We finally left Africa around 75,000 years ago and spread around the world. All modern non-African humans are descended from this group.
It seems that homo sapiens is quite malleable.
Apart from what you refer to as races [ various skin colourations and minor physical differences] different groups have also recently developed, to varying degrees, alcohol, lactose and gluten tolerance. Gluten tolerance can only have arisen since the development of farming gluten rich cereals such as wheat within the last 5000 – 6000 years.
Lactose tolerance in adults is a very recent development. Even 2000 years ago most European adults were lactose intolerant.
So we can change, and do change [evolve] , quickly in evolutionary terms
Humans are evolving rapidly at the moment, thanks to rapid population increase in recent generations, despite no longer being as geographically isolated as previously (before c. AD 1500).
In the archeology paper, is there a corresponding author who can be emailed for answers or can one write to the journal with a criticism that the temperature conditions in the Eemian should have been mentioned in such a scientific paper – such an omission is egregious.
“….and responses of interlinked human and natural systems”
??? Are we not natural, including our nature?
I just looked up, Eemian in Wikipedia and I was surprised. How long until it is rewritten?
Wow, and all this time I was taught it was the land bridge caused by the last glaciation that allowed humans to spread around the globe.
Coming to the Americas is different from leaving Africa.
The Toba volcanic eruption in Indonesia has been dated at around 70,000 years BP; coincidentally, human DNA suggests that humanity was almost wiped out around that time. What are the odds of the two events being totally unconnected?
Nice idea, the problem is the data don’t support your hypothesis.
http://www.cs.toronto.edu/~sme/PMU199-climate-computing/pmu199-2012F/notes/wk1/Young-Steffen-Fig14.1b-l.jpg
IMO the Aborigines’ arrival in Australia is too early on that graph.
Earliest good evidence of human presence on Australia is from c. 55 Ka:
http://australianmuseum.net.au/the-spread-of-people-to-australia
More than 60 Ka is possible of course, but there’s no good evidence to support a date that early.
The first migration of fully modern humans from Africa happened at least 120,000 years ago, as proven by the Skhul and Qafzeh fossils.
By the way most things in that chart are wrongly dated. As already noted, no evidence that humans were in Australia that early. On the other hand modern humans were in Central Asia by at least 45,000 years ago while there is very little evidence of their presence in Europe much before 40,000 years ago.
And agriculture starts much earlier, during the Younger Dryas, c. 12,000 years ago.
Early human migrations:
http://humanorigins.si.edu/sites/default/files/imagecache/inline_blog_portrait/images/portrait/3.3.4-30_handaxe_bose_jdhd_p.jpg
Handaxe from Bose, China, about 803,000 years old.
“A huge meteor impact occurred in the atmosphere near China 803,000 years ago and the shock caused earth rocks to melt and explode, forming tektites. Widespread forest fires followed. Shortly after, humans moved into the barren landscape and scavenged for resources.”
=================
The story goes that those antique humans were wiped out and replaced with another migratory wave of “modern” humans from Africa ~50,000 years ago.
But on what evidence?
Why do human tribes exhibit so many physiological and cognitive differences, and why do we have to pretend that they don’t?
“Race” is indeed a social construct, but with a genetic basis.
As stated previously, humans don’t have true races, as do some other mammalian species. There obviously are superficial differences among geographic populations, but they’re not significant enough to qualify even the most unusual groups as subspecies, ie races in a biological sense.
However, in the US and elsewhere, there is a sociological construct commonly called “race” which is based upon those superficial differences in appearance and cultural traits associated with them at some more or less statistically significant level.
Thanks Sturgis.
Skin color is literally superficial. But there are physiological differences between tribes that go much deeper. For example, the list of “essential” amino acids for some “populations” is different to that of others.
~~~~~~~~~~~~~~~~~~~~~~~~
What Is an Essential Amino Acid?
This is an amino acid that the body cannot synthesize on its own, so it must be obtained from the diet. Because each has its own physiology, the list of essential amino acids is different for humans than it is for other organisms.
[…]
[And yet…] Certain populations [of humans] need [in addition to the common “essentials”] arginine, cystein, glycine, glutamine, histidine, proline, serine and tyrosine because they either cannot synthesize them at all or else are unable to make enough to meet the needs of their metabolism.
http://chemistry.about.com/od/lecturenoteslab1/a/Essential-Amino-Acids.htm
===================================
That kind of difference implies a long term isolation from common ancestors. “Race” may be a “social construct” of sorts, but it is based on the recognition of real differences between tribes.
Vive la différence!
The story goes that those antique humans were wiped out and replaced with another migratory wave of “modern” humans from Africa ~50,000 years ago.
But on what evidence?
DNA, both nuclear and mitochondrial.
Why do human tribes exhibit so many physiological and cognitive differences, and why do we have to pretend that they don’t?
Whose pretending that? For example, Andamanese and Papua New Guinea natives share the same allele (at MC1R) for melanin production with africans, europeans and east asians share genes with neanderthals for adaptation to non-african conditions (skin and hair).
tty July 6, 2015 at 12:06 pm
The first migration of fully modern humans from Africa happened at least 120,000 years ago, as proven by the Skhul and Qafzeh fossils.
The evidence is that this group either died out or returned to africa and was not the source of a permanent migration from africa. The coastal migration at a time of significantly lower sea level at about 65,000 ya is the most likely source.
Khwarizmi
July 6, 2015 at 8:55 pm
Mutations in protein metabolism are common.
Depending upon differences in diet, mutations might not affect various populations equally.
Didn’t the rain band move north about 5k years ago due to the earths axis creating the Sahara desert and aren’t they supposed to move back in another 5k and green it up again?
The Eemian was several degrees warmer than today? I see 8 degrees C warmer mentioned for Greenland, but not a number for global temperature. Meanwhile, most things I see indicate that global temperature during the Eemian peaked out at briefly about 3 degrees C warmer than current baselines, and had extended warm times about 1 degree C higher than warmer sustained times of the Holocene, which were about 1 degree C warmer than current baselines.
The Eemian was warmer than the Holocene and lasted 5000 years longer than our current interglacial so far, yet the Greenland Ice Sheet remained intact. Its Southern Dome lost some mass, but that was it.
So, is there any evidence (other than models) that 2 degrees of warming will harm the planet as much as alarmists insist it will? Data from the past seem to indicate that a little warming may be net beneficial. So isn’t this question still open to debate? At the very least, you would have to admit that the evidence for disaster is inconclusive. So how do warmists get away with pretending it is settled science?
Louis
‘The science is settled’.
So Nobel Laureates – like Mann, and me [I was in the EU or a citizen of it, or something, when it won a bauble for something – talking about stopping the Srebrenica massacre, was it?] – need not research any more.
But –
Can I have a bit of his funding – pretty please?
It is known.
Tablets of Stone.
[lousyrhyme-after-lousyrhyme (C)] [Soz!! Sorry to the rhymester!]
Auto
Didn’t know that the Eemian was named after the Eems river, which in the North of The Netherlands forms the border with Germany. There is a lot of literature which shows the findings in the sediments of the river bed which can be traced back to the previous interglacial.
This time Wiki indeed is a good source:
https://en.m.wikipedia.org/wiki/Eemian_interglacial
“This time Wiki indeed is a good source”
Not really, there are several errors in it.
It’s not the Mikulin interglacial in Russia, it is called Mikulino.
“The Eemian climate is believed to have been about as stable as that of the Holocene”
Wrong. There was a very marked cold interval with significant sea-level drop (=glaciation) in the mid-Eemian.
“global annual mean temperatures were probably similar to those of the Holocene”
Since we know that most of the Earth was significantly warmer this would mean that there must have been some large areas that were markedly colder than now. Very odd that we haven’t found any of them yet.
“North Cape, Norway (which is now tundra)”
Wrong. Alpine heath.
“The hippopotamus was distributed as far north as the rivers Rhine and Thames.”
True as far as it goes, but hippopotamus actually occurred as far north as Yorkshire (Victoria Cave)
“Hardwood trees such as hazel and oak grew as far north as Oulu, Finland.”
Also true as far as it goes, but hazel occurred as far north as Svappavaara, 300 km north of Oulu and well north of the Arctic Circle.
“south of the Alps, conditions were 1–2 °C cooler than today”
No evidence for this except in computer models. Tropical mollusks actually occurred in the Mediterranean, the well-known “Strombus” or “Senegalese” fauna.
“Scandinavia was an island due to the inundation of vast areas of northern Europe and the West Siberian Plain”
You always see this mentioned about the Eemian. However it was only true for a brief interval at the beginning of the interglacial.
tty
Thanks – your point about the plu-perfect paragon – ahhhhh you’ve read the rest. Wiki-perfection can start you off – but I tend to add a little disclaimer . . . .
Mods – careful – there may be a hint of sarcasm about the paragon in there.
Thanks!
Auto
Thanks tty,
Always nice to see that someone has better information than Wiki… Even so it is quite a miracle that the Wiki article was already admitting that it was (at least partly) warmer than now and wasn’t “corrected” by William Connolley…
Ferdinand
This article fails on many levels. As any good researcher will tell you, you have to look in the past to understand the future! The issue today is: Accelerated global warming/climate change as a result of the increased use of unsustainable fossil fuels and the destruction of the very thing that mitigates poor air quality at alarming rates.
I’m not sure who funds this article but in my honest opinion it is a poor reflection on the main issues facing biodiversity on the blue planet.
adam better to hide and just listen for a while, I’m sure there some skepticism in there somewhere…Perhaps you’ll eventually have an epiphany.
My take on how non-Neanderthals finally managed to handle European glaciation post-Eemian: they developed sewing, and could laugh at cold. As Eskimos etc. still do.
IMO the oldest needles known date only to Solutrean time, at the last glacial maximum. I might be outdated, however.
My guess is that prior modern human cultures used awls to make holes, then ran sinew through them rather than sewing garments. My impression is that Neanderthal clothing was more rudimentary, consisting of hides tied on or together in ad hoc ways.
Oops, meant after the last but one glacial retreat
getting back to my earlier comment, its a wonder given the large variety of skin pigmentation that there is no historical record of either blue peoples or green peoples even orange peoples seem to have missed the basket. Perhaps those self identifying as greenish people may eventually reached an enlightened skin pigmentation or use some chemical injections to augment nature.
Green men (whether little or large) may come to pass.
Why not add chloroplasts to human egg cells, so that we can produce our own sugar when exposed to light, provided our CO2 exhalation be somehow recycled into our cells rather than released at 100 time ambient concentration (contrary to the laughable lie of the Skeptical Science site maintained by a cartoonist who likes to dress up like a N@zi).
Last sentence should end with a question mark.
The “out of Africa” human migration story is based on the fact that Africans have far more mutations [than] other people, but few people are willing to consider the other possibility that also fits the evidence, that they simply mutated faster than other people. And the accepted supposition is “supported” by a lack of evidence.
On the contrary, the ‘out of Africa’ theory is well supported by the genetic data and is the prevailing view based on the preponderance of the evidence. The multiregional hypothesis does have some supporters but fewer than previously and in a weaker form, due to improvements in the genetic data available (mostly these days it persists in Chinese groups partly motivated, apparently, by Chinese nationalism). The prevailing current position is of several out of africa migrations with limited interbreeding with extinct archaic humans, neanderthal and denisovans, for example, in particular this appears through persisting immune system genes.
The “preponderance of the evidence” claim for that is largely based on the fact that Africans have far more genetic diversity (mutations) than all of the other populations combined and thus on guesses about mutation rates.
It assumes that every population had the same molecular clock, which means that every population had exactly the same repair enzymes, their environments were the same, population sizes were the same, average age of marriage was the same, and family sizes were the same. But we know these things aren’t true.
Larry,
The strongest evidence for the recent out of Africa hypothesis (where recent means 60-125 Ka) is the fact that all non-African mtDNA descends from the L3 haplogroup.
But there is also good supporting evidence in favor of this hypothesis.
Whether the bearers of this haplogroup left Africa just once, via the Red Sea crossing, or multiple times, to include via the Sinai, remains an issue. If a great many bands entered Eurasia, however, more haplogroups should be represented outside Africa.
Sturgis,
According to the most popular hypothesis, mitochondrial L0 gave rise to L1 and L2, then L2 gave rise to L3, which gave rise to M, N and R. But this hinges on the assumption that the molecular clock in every population runs at the same rate, then the population with the most mutations is inferred to be older. Since Africans (L) have the most mutations, they are inferred to be the oldest, so everyone else derived from them.[1]
However, the underlying assumptions about the shared common molecular clock rates are false.[2][3][4]
1. http://mbe.oxfordjournals.org/content/24/3/757.full.pdf
2.https://www.africandna.com/adna_static/ScienPapers/Do_the_Four_Clades_of_the_mtDNA_Haplogroup_L2_Evolve_at_Different_Rates.pdf
3. http://www.nature.com/hdy/journal/v101/n2/full/hdy200852a.html
4. http://www.nature.com/scitable/knowledge/library/neutrality-and-molecular-clocks-100492542
If anyone can be bothered, the “out of africa” therory is practically proved with mDNA. My mDNA can be traced to africa. Inhereted from our mothers. And so too does yours. So far there is no other theory to dispute that!
As noted just above, the Out of Africa hypothesis was based on assumptions about generic clocks that have been falsified by the mtDNA data.
WUWT readers shouldn’t be strangers to the many reason why certain ideas remain popular with some scientists, even after having been refuted by that data. Among those reason are politics, funding, inertia and egos.
By the way, everyone who takes a DNA test is now told that their ancestors ultimately trace back to sub-Saharan Africa, but that isn’t based on any analysis of inherited STR markers. It’s based on the assumption that the Out of Africa hypothesis is true.
In fact, unless you’re directly descended from a black African, you don’t share mutation markers with any sub-Saharan African haplogroups, which is why you don’t see any percentage of your actual ancestry showing up down there.
Yes you do. It ls in mDNA, inherited from mothers.
I say this because I have been tested over the recent 5 years for various genetic disorders by some of the best genetisists in Aus. My sister too has been tested by one very prominent genetisist in England. We know our DNA roots.
Patrick,
By saying that our mitochondrial DNA proves that we’re all descended from sub-Saharan Africans, they’re assuming that (among other things) the mtDNA mutates at the same rate in everyone, but that’s been proven to be false.
If the assumptions upon which the inference was based is false, then the inference fails. We may all be descended from southern Africans, but the data doesn’t currently support that hypothesis. Many people still support it, but the data doesn’t.
Yet another warm period, apparently, is the Hypsithermal Interval (http://glossary.ametsoc.org/wiki/Hypsithermal_period) , from 7000 to 500BC.
It is commonly said that tribal people have occupied southern Vancouver Island for 4000 years, which goes back into that era, but on the mainland perhaps three times that long.
Just a note, unsure what it might mean.