It has been argued (unsuccessuly) that the current change in climate will cause millions to billions of “climate refugees”. Some of these claims have been so “over the top” that they were quietly withdrawn and swept under the rug. Here, we have a real case of climate refugees based on natural variation of the climate.
From the UNIVERSITY OF ARIZONA and the “natural variation before the SUV is wot dun it” department:
Ancient humans left Africa to escape drying climate
Humans migrated out of Africa as the climate shifted from wet to very dry about 60,000 years ago, according to research led by a University of Arizona geoscientist.
Genetic research indicates people migrated from Africa into Eurasia between 70,000 and 55,000 years ago. Previous researchers suggested the climate must have been wetter than it is now for people to migrate to Eurasia by crossing the Horn of Africa and the Middle East.
“There’s always been a question about whether climate change had any influence on when our species left Africa,” said Jessica Tierney, UA associate professor of geosciences. “Our data suggest that when most of our species left Africa, it was dry and not wet in northeast Africa.”
Tierney and her colleagues found that around 70,000 years ago, climate in the Horn of Africa shifted from a wet phase called “Green Sahara” to even drier than the region is now. The region also became colder.
The researchers traced the Horn of Africa’s climate 200,000 years into the past by analyzing a core of ocean sediment taken in the western end of the Gulf of Aden. Tierney said before this research there was no record of the climate of northeast Africa back to the time of human migration out of Africa.
“Our data say the migration comes after a big environmental change. Perhaps people left because the environment was deteriorating,” she said. “There was a big shift to dry and that could have been a motivating force for migration.”
“It’s interesting to think about how our ancestors interacted with climate,” she said.
The team’s paper, “A climatic context for the out-of-Africa migration,” is published online in Geology this week. Tierney’s co-authors are Peter deMenocal of the Lamont-Doherty Earth Observatory in Palisades, New York, and Paul Zander of the UA.
The National Science Foundation and the David and Lucile Packard Foundation funded the research.
Tierney and her colleagues had successfully revealed the Horn of Africa’s climate back to 40,000 years ago by studying cores of marine sediment. The team hoped to use the same means to reconstruct the region’s climate back to the time 55,000 to 70,000 years ago when our ancestors left Africa.
The first challenge was finding a core from that region with sediments that old. The researchers enlisted the help of the curators of the Lamont-Doherty Core Repository, which has sediment cores from every major ocean and sea. The curators found a core collected off the Horn of Africa in 1965 from the R/V Robert D. Conrad that might be suitable.
Co-author deMenocal studied and dated the layers of the 1965 core and found it had sediments going back as far as 200,000 years.
At the UA, Tierney and Paul Zander teased out temperature and rainfall records from the organic matter preserved in the sediment layers. The scientists took samples from the core about every four inches (10 cm), a distance that represented about every 1,600 years.
To construct a long-term temperature record for the Horn of Africa, the researchers analyzed the sediment layers for chemicals called alkenones made by a particular kind of marine algae. The algae change the composition of the alkenones depending on the water temperature. The ratio of the different alkenones indicates the sea surface temperature when the algae were alive and also reflects regional temperatures, Tierney said.
To figure out the region’s ancient rainfall patterns from the sediment core, the researchers analyzed the ancient leaf wax that had blown into the ocean from terrestrial plants. Because plants alter the chemical composition of the wax on their leaves depending on how dry or wet the climate is, the leaf wax from the sediment core’s layers provides a record of past fluctuations in rainfall.
The analyses showed that the time people migrated out of Africa coincided with a big shift to a much drier and colder climate, Tierney said.
The team’s findings are corroborated by research from other investigators who reconstructed past regional climate by using data gathered from a cave formation in Israel and a sediment core from the eastern Mediterranean. Those findings suggest that it was dry everywhere in northeast Africa, she said.
“Our main point is kind of simple,” Tierney said. “We think it was dry when people left Africa and went on to other parts of the world, and that the transition from a Green Sahara to dry was a motivating force for people to leave.”
###
This 80’s song seems both prescient and appropriate, especially the part about the rains.
Another plausible group of climate refugees are the Cimbri, who abandoned their homes in Jutland most likely after a catastrophic storm tide:
Strabo probably couldn’t know that the North Sea causes frequent catastrophic floods that drowned people by the thousands.
During the time when so much water was locked up in the Arctic glaciers and the Sea level was hundred(s) of feet lower, there would also have been land bridges at what is now the Strait of Gibraltar, the Bosporus, and the Bering Strait. There would have been no water in what is now the Red Sea or the Black Sea. I think that we make the mistake of looking at the map the way it is now instead of how it would have been then.
Less water would have made the living harder in places, but less water would have made the migrations easier.
Recommended reading: “Noah’s Flood” by William Ryan & Walter Pitman
Bering strait, for sure. Max depth 160 feet. Allowed Siberians to become Amerinds by walking. Bosporus, for sure in places, max depth 120-420 feet. Facilitated migration from central Asia to Europe by walking. Also for sure Sunda in Indonesia, and English channel north end at Dogger Bank.
Strait of Gibralter, no way. Max depth 900 meters or ~3000 feet.
Correct. Gibraltar, NFW.
I’ve read that the Black Sea was a freshwater lake during this time, some 300 to 400 feet lower in elevation than present.
Not freshwater, since no outlet, like the Great Salt Lake.
Yes, freshwater. River inflow being greater than evaporation.
If you say so, but the LGM was dry. Also cold of course, slowing evaporation.
The Red Sea has never been dry during the Pleistocene, sea level was apparently never quite low enough, though the Bab el Mandeb must have been quite narrow during maximum glaciations.
Yup. Its central channel is about 250 m deep, but falls off steeply on both sides from ~40 to 60 meters deep on the continental shelves. The channel is around six miles wide at its narrowest. Maybe less. At the LGM, it would have been only some 110 m deep. In places there would have been 80 cliffs, but no doubt paths down to the water existed.
Eighty meter cliffs.
This was certainly NOT the “only” climate change causing shifts in human populations. Each glacial period undoubtedly forced many human groups to leave glaciated areas. It’s hard to make a living on glaciers. Also, parts of the Saharan Desert were much wetter during the Holocene Optimum and supported savanna fauna and human populations that had to migrate out of the region when it later turned into the present desert. I suspect there are many other examples. Humans in the past were very good at adapting when populations were relatively small. However, the next glacial period will likely create massive havoc unless humans find a way to prevent it.
This research from Arizona University is important new knowledge fitting in well with what is already known about the modern human out-of-Africa migrations.
This figure posted above by Vukcevic shows that the majority of the last glacial interval was characterised by dramatic, often violent excursions of climate change, such as the Dansgaard-Oescher “micro-interglacials”.
Evolution researchers consider that the frequent wide climate oscillations over the whole of the Quaternary glacial age, with biomes in Africa alternating between forest 🌳 grassland and desert 🌵 has played a crucial role in human acquisition of intelligence and tool use, since these were needed to adapt and survive. If you weren’t a crocodile.
The number one cause of Catastrophic Anthropogenic Climate Change are social justice adventures (i.e. elective wars, regime changes). Well, two. The need to obfuscate the environmental disruption by proponents of “clean” wars, and an unprecedented loss of life in a-abortion chambers operated by national and international socialists, is a first-order forcing of CAIR (Catastrophic Anthropogenic Immigration Reform).
The number one cause of Catastrophic Anthropogenic Climate Change are social justice adventures (i.e. elective wars, regime changes). Well, two. The need to obfuscate the environmental disruption by proponents of “clean” wars, and an unprecedented loss of life in a-bortion chambers operated by national and international socialists, is a first-order forcing of CAIR (Catastrophic Anthropogenic Immigration Reform).
Um, what has happened when the lands currently called Camada, the UK, Russia, Sandinavia etc. were covered by ice? I suggest people probably had to move south, as will we, in just a few thousand years with only a few hundred years warning, Crisis, disaster, catastophe, AKA natural long term climate variability..
brianrlcatt
No, I’m going to disagree with you here about this most recent Western Hemisphere Ice Age refugees.
Granted, they “probably” left Siberia trying to find new lands for grazing and hunting – though they left Siberia in the midst of the Ice by traveling “north” towards Alaska and the Bering Strait seafloor uncovered BECAUSE the western hemisphere glaciers and ice mass reduced sea levels enough to cross over “safely” .
But the first humans arrived in North America (and promptly killed off all large mammals living here!) during the depths of the Ice Age around 12,000 – 13,000 years ago. If they were driven from Asia because of the Ice Age, they were “refugees”. If they left Asia and North Europe like the Huns, Visigoths, Goths, Franks, and hundreds of other tribes (followed later by the Mongols) did between 150 and 500 AD, they were conquorers and invaders. Forced out by climate perhaps, but certainly not “refugees”!
RACookPE1978 October 5, 2017 at 4:09 pm
brianrlcatt
No, I’m going to disagree with you here about this most recent Western Hemisphere Ice Age refugees.
Granted, they “probably” left Siberia trying to find new lands for grazing and hunting – though they left Siberia in the midst of the Ice by traveling “north” towards Alaska and the Bering Strait seafloor uncovered BECAUSE the western hemisphere glaciers and ice mass reduced sea levels enough to cross over “safely” .
Recent work has shown that the first arrivals were probably by boat before the ice-free corridor became passable.
See Science, 11 Aug 2017, pp542.
Don’t agree that people lived on the ice cap from choice. What do they live on and how do they shelter and stay warm on an ice cap? Which reached 50 degrees latitude?
Unlikely, if there was land , animals and fish further south. Migration was how hunter gatherers lived, they wre not settled. Where does their personal and heating energy come from? No enrgy, no life. What lives on land covered in ice sheets? People would move unless trapped when the ice came, or face life on very thick and inpenetrable land ice where there is nothing to grow or growing, or to hunt or fish. What I suggested is what the record appears to show. The means of transport around the Pacific rim is now suggested to be probaly water, coastal navigation, too hard on land, and that probably happened in the previous interglacial, land bridges not necessary, although the Bering straight is only 50 metres max deep, so crossable in an ice age, but maybe that wasn’t the route? Alaska is no fun to traverse.
Note the Polynesians could cross the open Pacific, if you have watched Moana you now that.The early migrations from Africa made it to South America this way, setting up coastal settlements on the way, nothing much to the East of the Andes/Rockies/Sierras. In S Smerica they finally met their brother met Cortez et al coming the otherway, same genes but one called the other primitive and massacred them for supposed gold. I don’t think it likely anyone tried to live in top of land based ice caps. Life was unsupportable then and even today requires constant supplying from ice free areas today. Illogical, Captain 🙂
They were driven South by the ice, so were refugees from it. People moving to refuge elsewhere from a problem where they were that was life threatening BTW.
I’ve been a climate refugee for most of my adult life, taking refuge in warm places during the northern winter. Then I flee the heat of those places.
When the climate changes, people really notice of their own accord and take appropriate action.. They do not need relentless propaganda from the media to notice real climate changes.
Did I read that right? They found only one core to study? If so, then this paper should not have been written until more data was available. While not quite in the category of Briffa’s one single tree, this study is similarly methodologically unsound. It is so typical of today’s science where it is all about getting as many papers out of as little data as possible. Publish or perish.
I might actually agree with the findings but that is merely a reflection of confirmation bias, not an indication of scientific validity.
Apparently
“Modern European and Asian people may owe more than skin or hair colour to Neanderthal ancestry. Matching modern genetic profiles against genes known to have been inherited from Neanderthals has shown links to a wide range of current disorders. ………… Our main finding is that Neanderthal DNA does influence clinical traits in modern humans. …. The brain is incredibly complex, so it is reasonable to expect that introducing changes from a different evolutionary path might have negative consequences”
claims Guardian
Now we know, all Euro-Asians depressed by prospects of ‘catastrophic global warming cataclysm’ are much closer to Neanderthals than previously thought, which is no surprise, the Neanderthals prospered during the last glacial.
Actually “bad” Neanderthal genes got selected out. There are so called “Neanderthal deserts”, i e parts of the modern eurasian genomes that contain no neanderthal genes at all. This is true e g for genes connected with language capabilities, suggesting that neanderthals were significantly inferior in this area. Neanderthal genes seem to be most common for genes that are connected with the immune system, which seems reasonable, the neanderthals probably had acquired resistance for a lot of nasty things that africans had never encountered before.
It must be somewhere in the Y chromosome. Large % of married women think their husbands are closely related to Neanderthals , while the the other way around is a rare exception. 🙂
Actually there are very few if any neanderthal y-chromosomes around. Male hybrids were apparently sterile or had very reduced fertility. The same is true for sapiens/denisova hybrids:
http://www.cell.com/current-biology/fulltext/S0960-9822(16)30247-0
By the way there is no Neanderthal mt-DNA around either. It seems that neanderthal genes were largely transmitted by daughters of a neanderthal father and a sapiens mother.
The other day I read that scientists have found ancient humanoid bones in Europe that bring the whole theory of the migration out of Africa into question. It seems the European bones are older than the African ones. I guess that blows the ‘left Africa due to climate change’
hypothesis out of the water. Oh well. Back to the drawing board.
A problem is both where people doing paleontology look for fossils, and sites with good fossils. There are a lot more people looking in places like Europe (or South Africa), so they should find more fossils. Then there is the issue of where such fossils could form, which might or might not correspond to where the hominids actually lived.
Those bones are actually late Miocene, about six or seven million years old. They might indicate that the common ancestor of humans and chimps immigrated to Africa from Eurasia.
This is not a new idea by the way. There is an interval during the Miocene when no hominine fossils are known from Africa, but they do occur in Eurasia, so it has been hypothesized that hominines became extinct for a while in Africa, which was then repopulated from Eurasia. But this was way back and does not affect the “out of Africa” paradigm in the slightest. That is just ignorant sensation-mongering journalism.
Never believe anything you read about scientific matters in the MSM, it is almost certainly either flat-out wrong or misunderstood.
Cally
You may be referring to research that found possible 6-7 million year old proto-humans in the Greece/Bulgaria/Turkey region. However back at that time there was no Mediterranean so this area would be continuous with North Africa. So the finding changed little regarding very early human origins.
If not for the out-of-Africa migration, there would be only one race – African. The races evolved as adaptations of humans to their local environment and climate. We have climate change to thank for the different races. We don’t want to be all Africans. That’s not a racist remark lol
Actually there is at least two quite distinct races in Africa south of the Sahara, the Khoisan and the “N-worders”.
IMO there are no human races at all, in the biological sense of subspecies. Humans show remarkably little genetic variation, despite a global distribution, compared for instance to chimps. Maybe a bottleneck from the Toba eruption accounts for this fact.
There are however genetically distinct groups, such as the Khoisan (“Bushmen”) v Bantus and other African populations, and those outside Africa.
Bantu is a language group, not a population. And you make a very common mistake, confusing raw genetic distance (which is almost exclusively a function of the length of time two populations have been separated) with significant genetic changes, which are subject to selection.
Most mutations have no somatic effect at all or are neutral from an evolutionary viewpoint. However it does not necessarily take very many mutations, or a very long time, for a subspecies or even a species to evolve. Especially if sexual selection is involved.
The raw genetic distances within Homo sapiens are small, yes, but the morphological differences between different subspecies are actually remarkably large, compared to most other mammals.Some subspecies are even osteologically determinable, i. e. can be identified on skeletal characters, which is quite unusual. Human subspecies differ significantly in a remarkably large number of ways: size, pelage color and structure, skin pigmentation, body proportions, iris color, tooth morphology, distribution of subcutaneous fat, cranial morphology, immune system characteristics etc etc.
And then there is a qualitative difference we didn’t even know about until recently. Africans are (almost) pure Homo sapiens, everybody else are hybrids of even triple hybrids.
And as mentioned above the sapiens/neanderthal/denisova hybridization shows that 500,000 years of isolation is enough to cause partial sterility in human hybrids, so 50,000 years is actually something like 10% of the way to a separate biological species.
Many of the races are related. Here’s my own classification based on physical appearance and ancestry. By coincidence, 7 is the ancient mythical number
1. African, Australian aborigine
2. Caucasian-European
3. Intuit, Mongolian, Native American, Aztec, Mayan
4. Syrian, Egyptian, Babylonian, Hebrew, Persian, Arab, Turk
5. Indian, Pakistani, Sri Lankan, Burmese, Bangladeshi
6. Chinese, Japanese, Korean
7. Polynesian, Malay, Indonesian, Cambodian, Vietnamese, Thai
All others are mixed races. Latinos are a mix of Caucasian and Aztec-Mayan. Mongolia is far from South America but in the last ice age, there was a land bridge in the Bering Strait. They probably originated in Siberia and migrated to North and South America. This ancient people were also the ancestors of Mongolians.
Many of the races are related. I counted 7 races based on physical appearance and ancestry.
1. African, Australian aborigine
2. Caucasian-European
3. Inuit, Mongolian, Native American, Aztec, Mayan
4. Syrian, Egyptian, Babylonian, Hebrew, Persian, Arab, Turk
5. Indian, Pakistani, Sri Lankan, Burmese, Bangladeshi
6. Chinese, Japanese, Korean
7. Polynesian, Malay, Cambodian, Vietnamese, Thai
All others are mixed races. Latinos are a mix of Caucasian and Aztec-Mayan.
Not by inferred ancestry, Africans are maximally distant from Australian Aborigines. By DNA variations, Africans have more diversity than all other groups, going off reports by Cavalli-Sforza. Dark skin developed several times, apparently.
Just like CAGW timelines and the length of time it takes for things to actually happen are far, far longer than the media and the CAGW crowd would have use to believe. Even if they are right and we will not know until most of us are gone, the CAGW crowd compresses timelines down to years, decades and elections cycles and have to a certain extent overplayed their hand. If it one does not let any “good crisis go to waste” the average person doesn’t see or care about crises beyond their lifetime, maybe their children’s. Having minored in anthropology and long discuss human and protohuman migrations there is little doubt that changes in climate played a role both in SLOWLY driving humans from one place to the next but in also providing new opportunities. A large percentage of humans are risk takers and explorers, they seek the unknown, what is over the next hill. That tendency probably evolved during our hunter-gather era. Of course a trait from that era that has gets us in trouble today is denial. Going up against large megafauna it was a required trait or we wouldn’t have eaten. Today it gets the average person in trouble daily.
Two words — denialist camps
These are places where catastrophic-climate skeptics can go to live climate-alarmist-free. They will be upscale, gated communities with tight security and strict ideological preferences, to insure that science is given a fair shake. No posters of Michael Mann allowed, … no visiting skepticalscience.com allowed – visited IP addresses are monitored electronically, and so anytime such a visit is detected, a community alarm goes off, alerting all community members to grab stones and clubs to correct the situation.
Yes, it’s extreme, but extreme stupidity calls for extreme measures.
Here in Scotland around 6,000 years ago, it is generally accepted that the climate cooled and got wetter, leading to the movement of people from higher altitudes to lower altitudes,
Yes, and there was a similar movement at the end of the MWP. In the Lammermuir hills the upper limit of cultivation sank 200 meters between 1300 and 1600.
Toto is a great band. Nice intro Anthony.