Guest commentary by David Middleton
From the No Schist Sherlock files…
PUBLIC RELEASE: 19-APR-2018
Humans have been driving a global reduction in mammal size for thousands of years
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
The dispersal of humans out of Africa coincided with a dramatic global reduction in the size of mammals, a new study reveals. This “downsizing” trend may continue, suggest the authors, to the extent that, in just a couple hundred years, the largest terrestrial mammal left may be the domestic cow, weighing in at 900 kilograms (kg). Felisa A. Smith et al. sought to understand how the size of mammals has changed over time. They updated and created two datasets that capture the global distribution and body size of terrestrial mammals that lived between 66 million years ago through the present. The authors found a substantial bias in mammal extinction during the periods when humans were dispersing around the globe, whereby species that went extinct tended to be two to three times bigger than mammals that survived, a trend that was evident globally. Notably, prior to humans’ migration out of Africa 125,000 years ago, Africa was home to mammals of smaller size (with a mean body mass roughly half that of mammals found in Eurasia), which the authors suggest is reflective of the hominin-mammal interactions that had already been at play. Perhaps most striking is the reduction of mammals in the New World during the late Pleistocene, which coincided with humans’ adoption of long-range weapons. The authors report a greater than 10-fold drop in both mean and maximum body mass of mammals during this time; for example, mean mass of terrestrial mammals in North America fell from 98.0 to 7.6 kg. If current trends continue, the mean body mass of mammals in North America will drop from 7.7 to 4.9 kg in a few hundred years, the authors say. As mammals play a critical role in shaping ecosystems, the downsizing trend will have a cascading impact on other organisms.
The paper is pay-walled. Here are a few highlights from the abstract:
- Today, it is well known that human activities put larger animals at greater risk of extinction.
- If the current trend continues, terrestrial mammal body sizes will become smaller than they have been over the past 45 million years.
- Since the late Pleistocene, large-bodied mammals have been extirpated from much of Earth.
- This decline is coincident with the global expansion of hominins over the late Quaternary.
- Moreover, the degree of selectivity was unprecedented in 65 million years of mammalian evolution.
- The distinctive selectivity signature implicates hominin activity as a primary driver of taxonomic losses and ecosystem homogenization.
And my comments on the highlights:
- They were in the way, some of them hunted us and most of them tasted good.
- Where do you think Chihuahuas, Pomeranians and Corgis came from? Besides, when was the last time a large mammal species became extinct? What percentage of megafauna bought the farm in the Early Holocene vs the fictitious “Anthropocene”?
- I’m sure we didn’t intend to extirpate most of them. My guess is that most of them were long gone before the word “extirpate” was invented. It’s highly likely that our ancestors used the word “eaten” in the early days of language.
- Are you saying we should have stayed in Olduvai Gorge? Or that we should have extirpated ourselves?
- Blame the dinosaurs. If they didn’t get extirpated. none of this would be happening.
- So what?
Is “the bleeding obvious” really a scientific discipline? Humans played a big role in wiping out 169 out of 244 genera of mammalian megafauna from the Late Pleistocene through the Early Holocene. This isn’t a eureka-worthy new discovery:
Here’s another gem from the Eureka Alert article:
Perhaps most striking is the reduction of mammals in the New World during the late Pleistocene, which coincided with humans’ adoption of long-range weapons.
What’s even more striking than most striking is that it was also coincident with human domestication of wolves. Dogs may have played an integral role in enabling humans to out-compete Neanderthals. Humans began the process of shrinking wolves between 20,000 and 40,000 years ago.
New data from ancient dogs indicates that dogs became distinct from wolves between 20,000 and 40,000 years ago, researchers report July 18 in Nature Communications.Dogs then formed genetically distinct eastern and western groups 17,000 to 24,000 years ago, the researchers calculate. That timing and other genetic data point to dogs being domesticated just once.
As early as 10,000 years ago dogs in the Americas were so valued as companions and fellow hunters that at least three of them were given proper burials rather than being eaten:
WASHINGTON — A trio of dogs buried at two ancient human sites in Illinois lived around 10,000 years ago, making them the oldest known domesticated canines in the Americas.
[…]
Ancient dogs at the Midwestern locations also represent the oldest known burials of individual dogs in the world, said Perri, of Durham University in England. A dog buried at Germany’s Bonn-Oberkassel site around 14,000 years ago was included in a two-person grave. Placement of the Americas dogs in their own graves indicates that these animals were held in high regard by ancient people.
An absence of stone tool incisions on the three ancient dogs’ skeletons indicates that they were not killed by people, but died of natural causes before being buried, Perri said.
[…]
So… Yes, “humans have been driving a global reduction in mammal size for thousands of years” and it had nothing to do with fossil fuels, CO2 or Gorebal Warming… Nor would renewable energy sources or a Tesla in every garage have prevented it.
Some of the big mammals wound up here:
And some wound up here:
The moral of the story: Big animals that chose to help us hunt fared better than those that didn’t.
Chicken v. egg. They’ve taken the side that because the extinction of some large mammals occurred during the period of human expansion, that humans were responsible. Try reversing the causation. The extinction of larger mammals enabled humans to expand into new territories. There is no evidence that early humans used poisoned weapons to kill large animals the way Bushmen in South Africa do when they hunt elephants, or indigenous people in the Amazon basin with curare and poison frog envenomed blow gun darts. Maybe they did that 100,000 years ago, maybe/probably not. But trying to kill mammoths with stone spears, or defend against cave lions, short faced bears and sabertooth cats is an extremely hazardous occupation. So which makes more sense? Small numbers of people moving into new territory as climatic conditions changed and facilitated the expansion, killed off the really big animals, or….those same climatic conditions reduced the population of the really large herbivores and carnivores, allowing little humans to move in without as much threat of getting stomped into a pancake or being the guest of honor at the sabertooth picnic.
The climatic changes at the end of the Pleistocene were no different than the climatic changes of the half-dozen or so previous deglaciations.
The transitions of the glacial cycles were probably challenging times for most megafauna. The influx of humans (and dogs) was probably the straw that broke the camelops’ back.
“The extinction of larger mammals enabled humans to expand into new territories.”
So you suggest that it was the extinction of the giant sloths and hutias that caused the colonization of the West Indies 4,000 years ago? Or that the extinction of Hippopotami and Giant Lemurs enabled the colonization of Madagascar 2,500 years ago?
By the way it won’t work for New Zealand which had no native mammals (except bats) and where the last Giant Moas can be found in the kitchen middens of the first maori.
And if you doubt that early humans could kill large animals google “Lehringen Elephant”.
My take on dogs: Humans didn’t domesticate dogs, the canine was intelligent enough to see the benefits of partnering with humans, and they domesticated humans. What other animal has so captured the love of humans than dogs. We walk them, pick up their waste, provide their health care, spend billions feeding them, and make they social media stars. And we’re supposed to have bigger brains? At my house, our dog is my wife’s best friend.
We have 10… More accurately they have us.
“What other animal has so captured the love of humans than dogs. ”
Cats. Except that people love cats even when the cats don’t give a damn.
We have never managed to domesticate cats. The cats have domesticated us.
The wolves that decided to hook-up with humans were the smart ones.
There are now more than 500 million of them, while the wolves are only 300,000.
Smart and not very demanding… At least not initially. The demanding bit changed.
One can smell the models in that ‘research’ from far away.
Another pathetic fake research where assumptions drove alleged research’s direction.
i.e. the authors set out to prove their what they already believed.
Assumptions filled in their preferred data.
Large animal bones are far easier to find, measure and count.
Medium and small animal bones are uncommon, far harder to locate, isolate measure and track. Especially animals that are consumed whole or in portions.
Very small animal bones are easily damaged from any handling.
Those very small, small and medium animals identified through their fossil remains are exceptions, not the rule. Accurate counts are impossible.
These researchers automatically assume people are the reason for animal extinctions.
Meaning, that they do not attempt to research why some large animals prospered.
Summing animals into some quasi average size estimates masks individual animal sizes, thus hiding animals that might’ve increased in size.
At the end of their research, “voilà!”; all correlations and associations are assumed to be cause and effect.
Another self satisfaction tinkering with formulas and models proving beliefs through gross assumptions.
The funniest part to me was when they explained that there is a greater environmental impact from small mammals because when large mammals go up a hill they zigzag whereas small mammals make a straight path, leading to greater erosion. You could not make this stuff up.
Hmmm. Just checking – is it the eco-loons that want to bio-engineer humans into a smaller-bodied species?
Didn’t they just put out a mainstream Hollywood production, acted and produced by the usual dunces?
Back in the fifties, ‘Dr Cyclops’ was a horror film.
Fast forward and it’s a progressive fantasy.
Now let’s make a graph showing devaluation of the US dollar vs CO2.
Carbon is shrinking the value of the dollar !
SOLUTION: Tax carbon, in order to produce more dollars lessened in value BECAUSE of carbon in the first place. Then create a new financial instrument based on debt accumulated by those who cannot afford to pay their carbon taxes. Carbon-debt futures, maybe ? I’m no economics expert, … obviously.
Mammals are getting smaller, while human egos are getting bigger. Anybody else see a causal relationship here?
I note that humans are relatively small mammals, so an increase in the number of humans will shift the average mammal size towards our size.