origin of humans; a new massive analysis (Origins)

by David Turell @, Sunday, April 28, 2024, 18:48 (46 days ago) @ David Turell

The original study:


The search for drivers of hominin speciation and extinction has tended to focus on the impact of climate change. Far less attention has been paid to the role of interspecific competition. However, research across vertebrates more broadly has shown that both processes are often correlated with species diversity, suggesting an important role for interspecific competition. Here we ask whether hominin speciation and extinction conform to the expected patterns of negative and positive diversity dependence, respectively. We estimate speciation and extinction rates from fossil occurrence data with preservation variability priors in a validated Bayesian framework and test whether these rates are correlated with species diversity. We supplement these analyses with calculations of speciation rate across a phylogeny, again testing whether these are correlated with diversity. Our results are consistent with clade-wide diversity limits that governed speciation in hominins overall but that were not quite reached by the Australopithecus and Paranthropus subclade before its extinction. Extinction was not correlated with species diversity within the Australopithecus and Paranthropus subclade or within hominins overall; this is concordant with climate playing a greater part in hominin extinction than speciation. By contrast, Homo is characterized by positively diversity-dependent speciation and negatively diversity-dependent extinction—both exceedingly rare patterns across all forms of life. The genus Homo expands the set of reported associations between diversity and macroevolution in vertebrates, underscoring that the relationship between diversity and macroevolution is complex. These results indicate an important, previously underappreciated and comparatively unusual role of biotic interactions in Homo macroevolution, and speciation in particular. The unusual and unexpected patterns of diversity dependence in Homo speciation and extinction may be a consequence of repeated Homo range expansions driven by interspecific competition and made possible by recurrent innovations in ecological strategies. Exploring how hominin macroevolution fits into the general vertebrate macroevolutionary landscape has the potential to offer new perspectives on longstanding questions in vertebrate evolution and shed new light on evolutionary processes within our own lineage."

Another commentary:


"In evolution, competition is thought to be a zero-sum game. One species adapts and survives. Another doesn’t and dies off. A new study in Nature Ecology & Evolution posits that human ancestors might be an exception.

"Conventional wisdom in evolutionary theory has held that climate has driven the rise and fall of various hominin species. In most vertebrates, interspecies competition also plays an important role. That role has been discounted in human ancestors, according to the study.

“We have been ignoring the way competition between species has shaped our own evolutionary tree,” said Laura van Holstein, a University of Cambridge archeologist and author of the paper, in a press release. “The effect of climate on hominin species is only part of the story.”


"Van Holstein found that in many early hominins — as in other mammals — separation into other species increases, then flatlines, at which point extinction rates start to ramp up.

"But when she looked at the later “Homo” groups of hominins, van Holstein noticed a finding she called bizarre. Her analysis showed that competition between Homo species appeared to result in even more species.

"'This is almost unparalleled in evolutionary science," van Holstein said.

"Her analysis explains why the hominin fossil record can sometimes appear uneven. Several more hominin species than previously assumed were likely co-existing, and potentially competing. She added that the fossil record, by itself, can’t fully explain separation into species, because it relies somewhat upon chance — the finding of a particular fossil that pinpoints a particular species to a certain time and place.

“'The earliest fossil we find will not be the earliest members of a species,” said van Holstein.

"So why the divergence? Later Homo sapiens became ecosystem engineers, according to the paper. Learning how to make and use tools and to build fires gave later species adaptive benefits that could improve quicker than any evolutionary change.

“'Adoption of stone tools or fire, or intensive hunting techniques, are extremely flexible behaviors,” van Holstein said. “A species that can harness them can quickly carve out new niches, and doesn’t have to survive vast tracts of time while evolving new body plans.'”

Comment: simple reasons we dominated. We outsmarted all of them!! Human exceptionalism, of course!

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