Bernard Wood: Understanding evolution is embracing weirdness – 10/30/2023 – Science

Paleoanthropologist Bernard Wood’s colleagues have a habit that often leaves him insulted.

“You know, everyone wants to find the first hominid [o mais antigo membro do grupo que inclui os seres humanos e não abrange os chimpanzés]. Sometimes you want to bang their heads together and scream: it’s not like that at all, you’re trying to force fossils into a classification that only takes modern species into account”, jokes the British researcher, who graduated in medicine in 1970 and worked as a surgeon before becoming one of the main scholars of human evolution in the world.

Wood was in Brazil this month at the invitation of the Institute of Advanced Studies and the USP Museum of Archeology and Ethnology. He gave two conferences in São Paulo and went out into the field in the region of Lagoa Santa (MG), in whose caves the oldest human skeletons in Brazil were found (up to 12 thousand years old). “Everything he published ended up becoming classics”, summarizes bioanthropologist Walter Neves, senior professor at the São Paulo university and one of those responsible for organizing Wood’s arrival in the country.

The Brit, who is now a professor at George Washington University (USA), has been working on three major fronts. The first is the study of the oldest hominins, those that may have lived around 7 million years ago, at a time when our lineage appears to have separated from that which would give rise to chimpanzees and bonobos.

The second is the emergence of the genre Homo (to which we, Homo sapiens, belong, and which is at least 2.5 million years old). Finally, Wood also usually analyzes the evolution of hominins of the genus Paranthropus. These extinct relatives of humanity could be roughly described as a bipedal, dwarf version of gorillas, thanks to their peculiar teeth and skull, adapted to large-scale consumption of plant matter.

“I lose interest as soon as hominins start to look like modern human beings”, explained Wood during his talk at the headquarters of Fapesp (Foundation for Research Support of the State of São Paulo). In addition to this prerequisite, the paleoanthropologist’s work has another main line: portraying the remote past of hominins with due complexity, and not as a simple prologue to the appearance of our species.

“The fossils that we find close to the divergence between hominins and chimpanzee ancestors will be really confusing, it’s something natural [pela semelhança entre as linhagens naquela época]. But the problem goes beyond that. Some of my colleagues imagine that all fossils that are 6 million or 7 million years old will either have some connection with hominins or with the ancestors of chimpanzees. But there’s absolutely no reason to believe that there couldn’t be an extinct lineage that didn’t correspond to either of them,” he explains.

A possible example is the species that, for some experts, would hold the age record among hominins: the primate known as Sahelanthropus tchadensis. “I have been a naughty boy when I talk about Sahelanthropus“, ironizes Wood. “But the fact is that perhaps the species would be much more interesting if we didn’t fit it into our lineage.”

On the other hand, the study of this very ancient phase in the evolution of the human lineage has been hampered by political and social instability in the regions of Africa that are home to rocks of the “right” age to find these fossils. Among the strategic areas, according to him, are Chad, South Sudan and Cameroon. Only the discovery of more fossils will be able to reveal the true diversity of great apes at that time.

Either way, says Wood, the best way to understand the evolutionary trajectory of hominins is to embrace its weirdness and get rid of the idea that it is a simple, linear sequence. “Our current situation is actually very strange, because it is the first time in several million years that there has been a single species of hominin,” he recalls. “The rule is that many species coexist inside and outside Africa.”

The study of gender Paranthropus is an excellent example of this logic. “Apparently, they fed on grass and reeds, which grow on the edge of bodies of water. It’s something that resembles part of the diet of some baboons today. Grass isn’t a very exciting business for us humans, but it happens that young leaves can be very nutritious”, he explains.

“As they are most likely not our ancestors, we tend to label them as failures or evolutionary dead ends, but the fact is that they survived for 2 million years, which is a considerable evolutionary success [o H. sapiens, por enquanto, só existe há 300 mil anos].”

Previously, it was believed that, in the Turkana basin, a region of East Africa rich in hominin fossils, the first members of the genus Homo moved more easily and took advantage of a wide variety of resources, as they were omnivores, while the Paranthropus it was a species that depended on less favorable environments.

But one of Wood’s graduate students is working on an entirely different hypothesis: the Paranthropus is that it would have occupied the Turkana basin first, having the most favorable habitats, while the first representatives of our genus would have been forced to “eat around the edges”, says the researcher.

And as for the oldest Homo, Wood is also skeptical of attempts to explain the origin of the genre based on a single factor, such as the increase in meat consumption or the manufacture of stone tools. “Every time someone proposes a simple solution to a complex biological problem, that solution is almost certainly wrong,” he says. “It is much more likely that a set of factors is behind the emergence of the genre Homo.”