No matter how you slice it, the discovery of a cache of ancient primate bones—about 15 whole skeletons' worth—in a cave called Rising Star about 30 miles from Johannesburg, South Africa is a major victory for science. Bold claims about the find abound: It's a unique new animal that looks to be from very early in human evolution, but it also appears to have buried its dead. This all has the scientists who discovered it urging us all to rethink much of what we know about human evolution.
"The new discovery is a new species—what we call Homo naledi," Jeremy DeSilva told VICE in an interview. DeSilva is an associate professor of anthropology at Dartmouth College who co-authored the paper on the discovery. He traveled to South Africa during the excavation to study just the legs and feet in the massive pile of newly discovered bones. "With this announcement, the entirety of the South African fossil record just doubled," DeSilva said.
Like most such finds, the cornucopia of bones has a grisly origin: Researchers think it was once a mass grave—although they've also entertained the idea that it was the site of a horrific accident.
But are they the bones of a whole new species? And does that even matter?
When the team of experts working on the find was still determining what they were looking at, DeSilva described a "mixed message coming from different parts of the skeleton." The fossils have legs like a modern human, he said, but an "almost ape-like" shoulder, hands that were a mix, of ape-like and human-like, and a tiny skull, only one third the size of ours. "So it was a combination of head-to-toe anatomies that led us to say 'Does this match anything that we know about?' and the answer is no, so you name it a new species."
Tim White, a UC Berkeley paleoanthropologist, and noted reconstructor of the "Lucy" skeleton, begs to differ. White told VICE in an email that "a new species name is not adequately warranted for the Rising Star fossils." Instead, he called Rising Star a "major discovery, whose significance lies in its potential to increase our biological understanding of a long-known, but still inadequately known species: Homo erectus."
You might remember the hilariously named homo erectus from that chart in high school biology (if you aren't from a creationist school district). In that tidy, linear presentation of evolution on a timeline, Homo erectus is a step between the knuckle-draggers and the almost recognizable human beings we might want to have a beer with.
It appears Homo erectus used tools, and since it covered a pretty wide geographical area, experts have long debated about what exactly this crazy extinct primate was. Maybe a direct ancestor of ours, and maybe not. Maybe even an entirely different genus.
White had strong words for the scientific rigor involved in calling this a new species, saying the paper's descriptions of defining traits are "simply mischaracterized on the fossils they illustrate," and that there are "traits whose differences from Homo erectus are exaggerated" along with "traits that are known to vary within a single extinct or living species such as Homo erectus."
In spite of White's harsh words about the paper, Desilva's response was surprisingly sanguine. "He might be right. This might be an early Homo erectus," he said. "The problem is we don't know what an early erectus looks like, and until we do, it's hard to match this against other specimens."
According to DeSilva, he best way to figure out where this species or subspecies falls on the evolutionary timeline is to date the fossils, and figure out when these creatures died. "If these are more recent, these aren't telling us about that older lineage. But if we get an older date, then potentially it is."
But that's really not a dismaying possibility at all, said DeSilva. If this turns out to be a Homo erectus, we'll know a whole hell of a lot more about the erratic course of human evolution. "I tend to think Homo erectus was kind of a singular species covering most of the globe for a long time, a single, evolving lineage, and then in Africa, erectus eventually evolved into Sapiens." By Sapiens, of course, he means us.
"What I tell my students is that in the early 1800s when only two fossils were known, you can play connect the dots between those very well, and human evolution is actually very simple, but wrong," he said. "A lot of recent discoveries have really shattered the idea of a linear progression of evolution—that classic chimp-to-human [image] that you see on t-shirts. That's just not how it happened."
When DeSilva says he wants to change how people think about evolution, the newly-discovered Homo naledi, and its time-bending combination of traits might be the perfect test case, regardless of whether it's a new species or not.
"Different aspects of our anatomy changed at different rates. If evolution can work in that kind of mosaic fashion—if you can get the foot and the legs and the hands and the head and the teeth, then you're going to have populations that actually have those features evolving in a disconnected kind of way," he said.
Maybe in the giant bucket of Lego pieces that makes up our DNA, there are castle parts next to elements of a spaceship, which are in turn next to the ingredients to make a race car. As paleontologists get an increasingly better view of history, they might see that evolution put a spaceship hyperdrive and a steering wheel on what we thought was Camelot, and it might blow their minds. That's what could be what's happening here.
"As a science, I think we need to stop being surprised by surprising discoveries," DeSilva said. "I think we need to expect it."
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