While we are "rethinking human evolution," let's rethink how we talk about human evolution

New human fossil finds are exciting, but don't always mean a new species has been found, or really "shake up the human family tree." Should discoverers be banned from studying their own fossils?

The Harbin, or “Dragon Man” skull / Ni et al.

“Oh no! Didn't we just ‘rethink evolution’ a couple of days ago? So now we have rethink it all over again?” — Michael Balter, commenting on a biological anthropology Facebook page.

Please forgive me for quoting myself just above, but I made this comment to a large group of biological anthropologists (including experts in human evolution) and it seemed to be appreciated. The context was a discussion of the latest, and quite spectacular, discovery of an early human, the so-called “Dragon Man” skull from China, found in Harbin City in the far northeast of the country.

My gently sarcastic comment was prompted in part by the headlines the discovery of this nearly intact (except for the lower jaw) skull generated.

“Discovery of ‘Dragon Man’ skull in China prompts rethink of human evolution,” NBC News declared.

“‘Dragon Man’ skull may be new species, shaking up human family tree,” wrote National Geographic.

“Massive human head in Chinese well forces scientists to rethink evolution,” The Guardian told us. (There we go, “rethinking” again.)

A little less hyped, but still emphasizing the possible evolutionary novelty of the discovery, was the headline in the New York Times: “Discovery of ‘Dragon Man’ Skull in China May Add Species to Human Family Tree.”

The discovery of any new fossils of early humans, or human ancestors, is always exciting, both for scientists and the public. And the Harbin skull, one of the best preserved ancient human crania ever found, is over the top fascinating in terms of what new information it might provide about human evolution (the skull, its provenance and dating, and its possible place on the tangled human evolutionary tree, are the subject of three papers in the The Innovation, a journal published by Cell Press in collaboration with the Chinese Academy of Sciences.)

But just a day or two earlier, another group of scientists, publishing in Science, announced the discovery of human fossils in Israel, at a site called Nesher Ramla. The fossils—a partial skull, a mandible (lower jaw) and a nice collection of teeth—were, the Times of Israel told us, “…’last survivors’ of ‘missing’ type of extinct humans.” The BBC’s headline was typical of many: “New type of ancient human discovered in Israel.”

I’m not sure if these headlines make the average reader dive into the stories to get all the details, or throw up his or her hands and conclude that it’s all too complicated. Certainly, in the 25 years that I have been covering human evolution, things have gotten much more complicated, due to a combination of many magnificent new fossil discoveries and—critically important—the advent of paleogenetics, the study of the DNA of ancient organisms.

This combination of hard work in the field and hard work in the lab has indeed given us important new insights into human evolution, even if we have long known the basic outlines: The human lineage arose from the apes, almost certainly in Africa, probably around 6 or 7 million years ago. Australopithecines, Homo erectus, some “archaic” Middle Pleistocene groups or species that researchers can’t agree what to call, then the Neanderthals, Denisovans, and Homo sapiens, with everyone else disappearing and leaving just us “modern” humans to rule the planet and perhaps wreck it for all the other species.

In a lot of ways, scientists are now filling in the details, which are fascinating in their own right, but not really “shaking up the family tree” or forcing researchers to “rethink” human evolution. These are clickbait headlines used by editors (journalists rarely write their own headlines, and when they do, few engage in this kind of hyperbole) and they both exaggerate and misrepresent what is really going on.

Take the new Harbin skull, for example. My favorite headline in all the news coverage is the one that Science used, in a piece by my former colleague Ann Gibbons: “Stunning ‘Dragon Man’ skull may be an elusive Denisovan—or a new species of human.” This headline actually puts the emphasis on what could turn out to be the greatest significance of the discovery, that it might finally put a face on the Denisovans, a group of early humans—closely related to both Homo sapiens and Neanderthals—that was identified strictly through analysis of ancient DNA from a finger bone that did not look that much different from the fingers of the other human groups.

Human evolution researchers have been searching for the actual fossils of Denisovans for a decade, because ancient DNA does not tell you what an early human actually looked like (although it can tell you the sex and the color of the eyes in some cases.) They finally got lucky a couple of years ago, when researchers studying a jawbone found more than 40 years ago on the Tibetan Plateau by a meditating Buddhist monk managed to extract some ancient proteins that matched the Denisovan profile. (The headline for Ann Gibbons’ writeup for Science, “First fossil jaw of Denisovans finally puts a face on elusive human relatives,” was a bit exaggerated, since our faces are more than just our jaws—but it may have been prophetic if the Harbin skull really is a Denisovan.)

But the Chinese team that published the Harbin skull prefers to designate it as a new species, which they call Homo longi (Long means “dragon” in Mandarin, thus the skull’s nickname.) In a commentary on the find, Chris Stringer, the famed paleoanthropologist at the Natural History Museum in London and a member of the research team, wrote that he could go either way—the face of a Denisovan or a new species—although if it is a new species, Stringer said, he would prefer to call it Homo daliensis, after a skull excavated in Dali, China in 1978, and to which the Harbin skull bears a close resemblance.

The Dali skull

Here is where, in my opinion, scientists are helping to enable those splashy headlines that must accompany any new fossil find if anyone is going to pay attention. You don’t get attention for your discovery if all you have found is yet another Neanderthal tooth among the thousands already discovered, even if that tooth might tell you something important about Neanderthal lifestyles and diet. (That gets you a paper in the Journal of Human Evolution, not Science or Nature.)

And since media attention and grant funding depend on producing results that really seem to make a difference, researchers not only tend to go for the most dramatic interpretation of their finds, but they also often hold on to their fossils for years without letting anyone else study them, or sometimes even see them. Not to be cynical, but the longer a scientist studies a fossil, it seems the more likely it is to end up being announced as a new species or some other kind of game changer for human evolution. And—based on my experience as a human evolution writer—the more likely it is that other researchers will turn around and challenge the interpretations.

I sometimes think that the discoverers of human fossils should be banned from studying their own finds for a certain number of years, until other scientists who don’t have skin in the game—or at least not quite so much—get to study them first. Scientists are human, after all, and the fact that they so often disagree about the meaning of a discovery strongly suggests that subjective factors often get in the way of the science—or, perhaps more accurately in light of the sociology and culture of research, are really part of the science and we don’t want to admit that.

The public, which ultimately funds the research, would benefit from this as well. They could be sure that when scientists and journalists say they are “rethinking” the human family tree, that tree is really shaking hard.