Researcher's paper challenges the claim that the genus Homo originated in response to environmental changes

August 4, 2017
Homo floresiensis adult female - model of head. Credit: John Gurche, National Museum of Natural History, CC BY-SA

An often cited claim that humans, who are smarter and more technologically advanced than their ancestors, originated in response to climate change is challenged in a new report by a Center for the Advanced Study of Human Paleobiology researcher at George Washington University.

Many scientists have argued that an influx, described as a "," of new animal species appear in the African between 2.8 and 2.5 million years ago, including our own genus Homo. Experts believe it takes a broad-scale event like global to spark the origination of so many diverse . However, W. Andrew Barr, a visiting assistant professor of anthropology, published a report that says it's possible the pulse of new species could have occurred by chance and might not be directly related to climate change.

It is generally accepted that when major environmental changes occur, some species will go extinct and others will originate, which can create a cluster or pulse of new species in the fossil record. However, there is not a set definition of what is considered a pulse, so experts have disagreed about which clusters constitute meaningful events and which can be explained as .

Dr. Barr used computer simulation to model what the fossil record might look like over time in the absence of any climate change and found clusters of originations that were of similar magnitude to the clusters observed in the fossil record. This means random patterns are likely under-credited for their role in speciation fluctuation, he said.

Dr. Barr's findings mean scientists may need to rethink widely-accepted ideas about why human ancestors became smarter and more sophisticated.

"The idea that our genus originated more than 2.5 million years ago as part of a turnover pulse in direct response to climate change has a deep history in paleonthropology," Dr. Barr said. "My study shows that the magnitude of that pulse could be caused by random fluctuations in speciation rates. One implication is that we may need to broaden our search for why our genus arose at that time and place."

He compared the pattern to flipping a coin. If you flip a coin 100 times, you would expect to record 50 heads and 50 tails. However, if you are only looking at 10 coin flips, you could see a greater imbalance, instead recording seven heads and only three tails. This would even out over time, but in the short-run, you could see clusters of these independent coin flips, he said.

Similarly, fluctuations in turnover in Dr. Barr's model are pronounced, but are caused purely by random processes.

"The idea the the origin of Homo is part of a climate-caused turnover pulse doesn't really bear out when you carefully look at the evidence and compare it against other possible explanations," Dr. Barr said.

This research challenges scientists to be careful about the stories they tell about the history of human adaption, Dr. Barr said. Traits that make humans different from our ancestors, like larger brains and greater technological sophistication, could have arisen for a variety of reasons, he said.

"We can sit in the present and tell stories of the past that make sense of our modern day adaptations," he said. "But these could have evolved for reasons we don't know."

The report, "Signal or noise? A null model method for evaluating the significance of turnover pulses," was published July 31.

Explore further: Fern fossil data clarifies origination and extinction of species

More information: W. Andrew Barr, Signal or noise? A null model method for evaluating the significance of turnover pulses, Paleobiology (2017). DOI: 10.1017/pab.2017.21

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the_bohemian_girl
1 / 5 (3) Aug 04, 2017
I haven't seen anyone groveling on about the loss of Neanderthals. You'll always be in my heart *insert Tim the Tool Man Taylor grunts*
TheGhostofOtto1923
2.3 / 5 (3) Aug 04, 2017
The genus homo originated as a result of tribal warfare and tech innovation. Tribes with a stronger tribal dynamic - internal amity coupled with external enmity - would consistently prevail in competition over resources.

'Prevailing' usually meant killing or enslaving all the males and incorporating all the females. As a result our brains were forced to grow at an unnatural and unsustainable rate.
TheGhostofOtto1923
2.3 / 5 (3) Aug 04, 2017
"Apparently Darwin had formed the opinion that natural selection acts to a great extent through intergroup competition. In his own words, "natural selection, arising from the competition of tribe with tribe,...would, under favourable conditions, have sufficed to raise man to his high position" (Darwin, 1871, i: 97).
This competition, in his opinion, could be carried out through direct conflict, even in bloody forms. "When of two adjoining tribes one becomes less numerous and less powerful than the other", he maintained, "the contest is settled by war, slaughter, cannibalism, slavery, and absorption". He was quite aware, however, that competition between groups had to be combined with cooperation within them (e.g., Melotti, 1987)"
http://rint.recht...rid2.htm

-Those with better strategies, better weapons, better communication and cooperation skills, better memories and better imaginations would consistently prevail over the competition.
Thnder
5 / 5 (2) Aug 04, 2017

-Those with better strategies, better weapons, better communication and cooperation skills, better memories and better imaginations would consistently prevail over the competition.

Those with the MOST cheese and the MOST pepperoni...
tblakely1357
1 / 5 (2) Aug 04, 2017
'When the only tool you have is a hammer, every problem looks like a nail.'
rrwillsj
2 / 5 (4) Aug 04, 2017
Oh man. here we go again! Dredging up Eighteenth and Nineteenth Century stupostitions in the smugly racist pseudo-science of eugenics.

The utter disaster of miss-breeding racehorses is just the most visible outcome of Calvinist/Presbyterian doctrines of Predeterminism and Predestination.

Next, I suppose you people will dig out your brass spirit horns to loudly proclaim the "Science" of Phrenology?
TheGhostofOtto1923
4 / 5 (1) Aug 04, 2017
Oh man. here we go again! Dredging up Eighteenth and Nineteenth Century stupostitions in the smugly racist pseudo-science of eugenics
What are you talking about specifically? Are you saying that group selection is racist but evolution is not?

Tribalism is undeniably racist. It means we are all inherently bigoted, and that egalitarianism is a learned behavior.

The perception of the universal tribe is exceedingly difficult to maintain and requires constant reinforcement. It also requires the constant reamalgamation of the species; constant displacement, the fracturing of households and communities, the constant encouragement of interracial comingling and the suppression of traditional cultural influence.

This is the real eugenics and it is taking place all around you.
Edenlegaia
5 / 5 (1) Aug 05, 2017
Oh man. here we go again! Dredging up Eighteenth and Nineteenth Century stupostitions in the smugly racist pseudo-science of eugenics.

The utter disaster of miss-breeding racehorses is just the most visible outcome of Calvinist/Presbyterian doctrines of Predeterminism and Predestination.

Next, I suppose you people will dig out your brass spirit horns to loudly proclaim the "Science" of Phrenology?


Too much elaborated words for so few valuable infos.
ddaye
not rated yet Aug 08, 2017
Tribalism is undeniably racist. It means we are all inherently bigoted, and that egalitarianism is a learned behavior.

I don't think it's a binary issue that must be either one or else the other. If individuals have a range of natural acceptance of extra-tribal strangers, there are probably situations where that's the advantage, others where tighter tribalism is the advantage. There's also the need to breed outside the tribe so we have to be at least a little accepting of novelty. My layman's bet is both traits are partly genetic and partly learned.

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