Everything Scientists Assumed About Human Evolution Needs a Major Rethink
by Jerry Bergman, PhD
So claimed a new article in the leading magazine New Scientist by Colin Barras,1 who says,“the story of human origins is being rewritten. The past 15 years have called into question every assumption about who we are and where we came from.” The article continues:
Until recently, the consensus was that our great march out of Africa began 60,000 years ago and that by 30,000 years ago, for whatever reason, every other human contender was extinguished. Only H. sapiens remained – a species with a linear history stretching some 6 million years back into the African jungle.
Starting in the early 2000s, Barras continues, new discoveries added layer on top of layer of complexity and confusion to the story of human evolution. Discoveries including, “Orrorin tugenensis, Ardipithecus ramidus, and Sahelanthropus tchadensis, pushed a long-held assumption about our evolution to breaking point.” Genetic work led scientists to believe that the human and chimp lineage split between 6.5 and 5.5 million years ago. These new discoveries looked more like us than modern chimps, indicating our lineage must be a million or more years older than previously thought. (One who follows human evolution stories knows that these date estimates change almost fast as the weather in my home state of Ohio.)
In 2012, revised ideas about how fast genetic differences accumulate forced another reassessment: the human-chimp split occurred between 7 and 13 million years ago, a range so wide that “guesstimate” is a more accurate word for these numbers. To confuse matters even more, earlier in the year, Professor Lee Berger announced the age of Homo naledi fossil remains from South Africa were a mere 236,000 to 335,000 years old. Then evidence broke that they were actually early members of H. sapiens, extending our species’ history back by a whopping 100,000 years.
It gets so bad that
there is no longer a clear consensus on how long hominins have walked the earth. Many are sticking with the old assumption, but others consider the possibility that the human lineage is almost twice as old, implying there are plenty of missing chapters to our story still waiting to be uncovered.
The belief taught in most of our textbooks is that our four-legged ancestors were forced out of the forests into desert conditions due to a drastic climate change, then evolved to walk on two legs. This is called the savannah hypothesis. But then, a skeleton first discovered in 1994, dubbed Ardipithecus ramidus (“Ardi” for short), claimed to be 4.4 million years old, challenged that view. (The claim that with Ardi paleontologists had finally found the ‘missing link’ is a tacit admission that they hadn’t found it before, in spite of numerous claims otherwise.) Actually, the new debate is more often a question of trying to settle internal conflicts within the community of evolutionary paleoanthropologists. The “true believers” in ape to human evolution keep changing their views with each discovery of new bones.
When examined, less than half of the Ardi skull fragments were found, leaving much room for speculation and interpreter bias. Its brain volume was estimated to be even smaller than that of a chimp. Nonetheless, paleontologists have tried to deduce much from the skeletal fragments found (for an illustration, see Anthropological Musings and Concepts Blog). Although often described as relatively complete, the fragments are probably close to 20 percent complete when measured by weight. The hand and foot bones were found, which allowed some scientist to conclude that Ardi didn’t swing below branches or knuckle-walk. This suggested to them that the ape which gave rise to chimps and humans may not have been very chimp-like. Thus, the idea—now more than a century old—that chimps are humans’ closest ancestors, is wrong. Evolutionists actually have no idea what the putative ape-human common ancestor looked like. Paleoanthropologists are not even sure if Ardi was a male or female.
Judging by its feet, legs and spine fragments, the creature was reasonably comfortable walking upright even though its discoverers claim that Ardi lived in a forest environment. But if that were true, it would mean that hominins began bipedal walking even before they left the forests – openly contradicting the savannah hypothesis.
Lucy no longer our arch-grandmother
After comparing another find, a skull called K. platyops, with those of other hominin species, some paleoanthropologists suggested that it was more closely related to humans than to any known Australopithecene. This had the effect of pushing the most famous pre-human fossil, Lucy, to a completely different branch of the hominin family tree. Then, the discoverers of a claimed 6-million-year-old hominin uncovered in 2001, called Orrorin tugenensis, had anatomy more human-like than the australopiths. To the true believers in human evolution, this meant it was more likely to be our ancestor than Lucy. All of this research may well expel Lucy—by far the most commonly-presented evidence of human evolution found in the school textbooks—from its iconic status. Now, a recent find of a human-like jawbone dated 2.8 million years old, discovered in Ethiopia, seems to be shoring up Lucy’s exalted position again.
In short, the paleoanthropology field is a confusing mess. Barras concluded that
Although weird bones have done their bit to question our human history, it’s the DNA inside them that may have done the most to shake up our evolutionary tree. With evidence of so much ancient interbreeding, it becomes far more complicated to decide where to draw lines between the different groups, or even if any lines are justified.
Exacerbating the problem is that DNA often profoundly contradicts the conclusions arrived at by phylogeny (building Darwin trees by comparing morphological traits). This all has caused some paleoanthropologists to change careers and become stockbrokers. In that field, they will earn more money and can escape from the sea of uncertainty inherent in trying to read old bone fragments. Nonetheless, Barras is an optimist, concluding having “dug ourselves into this philosophically troubling hole, there’s probably only one way to find our way out again: keep digging for fossils and probe them for more DNA.”[vii] So far, they have only been digging themselves deeper into the hole.2
- Colin Barras. Losing the Plot. New Scientist. August 26, 2017, pp. 28-33 (online article appeared August 23).
- Law of Holes: “If you find yourself in a hole, stop digging.”
Dr Jerry Bergman, professor, author and speaker, is a frequent contributor to Creation-Evolution Headlines. See his Author Profile for his previous articles.