The questions kids ask about science aren’t always easy to answer. Sometimes their little brains can lead to big places that adults forget to explore, and that’s what inspired our series Science Question From A Toddler, which uses kids’ curiosity as a jumping-off point to investigate the scientific wonders that adults don’t even think to ask about. The answers are for adults, but they wouldn’t be possible without the wonder that only a child can bring. I want the kids in your life to be a part of it! Send me their science questions and they may serve as the inspiration for a future column. And now, our toddler …
“Who took care of the first baby?” —David B., age 5
The trouble with this extremely good question is that it presupposes we know facts we do not actually know. Or, as Tim White, a helpful and not-at-all sardonic paleoanthropologist at the University of California, Berkeley, put it, “Good luck finding the first baby!”
His point is that the chain of evolution is long and has no clear beginning. It’s easy to look at the fossil record and sort what you find into categories of “human” and “not human,” but that comes from the vantage point of hindsight. (And even that categorization isn’t really all that easy. But we’ll get to that later.)
In the moment nobody would have known any specific baby was the first human. There was never a day when an ape-like Lucy the Australopithecus gave birth to a human baby and everybody was like, “Whoa! What the heck is up with THAT kid!?”1 There wasn’t even a moment when our more closely related immediate ancestors, Homo erectus, were standing around staring at a Homo sapiens baby. Instead, it’s more like when you spot the first buds on trees … and then look around one day and realize spring is in full bloom. It didn’t happen overnight. There was a slow, gradual change.
The job of sorting living things into separate tidy categories is simultaneously valuable science … and also kind of a load of pure applesauce. The idea of “species” originally came from a time before the theory of evolution had been pieced together. Carl Linnaeus and the other European protoscientists believed that the Christian God had created animals, plants, and humans in their current forms — each species clearly distinct from one another.
But taxonomy, like the things it classifies, has evolved. Part of that evolution is the recognition that the boundaries between species are actually pretty messy. The ways we visually identify a species aren’t fixed — over a few generations, animals will change behavior and appearance if they move somewhere new or if the places where they live change. When that happens, are they still the same species?
Likewise, in school, you may have learned that different species can’t produce viable offspring together. And, yet, animals of different species are often able to interbreed. (Consider the liger.)
“Rigid classification doesn’t reflect dynamic evolution, it just can’t be done,” White said.
And if classifying living, breathing animals into clear and obvious species is that complicated, imagine trying to do it with the fossil record, where you may have only a couple of incomplete specimens of any given possible species. To take one tiny group of fossils and compare them with another and decide, yeah, we all pretty much agree those are two different species “can sometimes take decades of uncertainty and debate,” said paleoanthropologist Rick Potts, who heads the Human Origins Program at the Smithsonian Institution.
In general, he told me, scientists distinguish between Homo sapiens and the not-quite humans who came before based on features like a rounded skull, “as opposed to something that looks longer and more drawn-out, with a low forehead,” Potts said. He also characterized Homo sapiens as having a distinctly small face that sits almost completely beneath the part of the skull that holds our brains. “Early humans, the face looks hafted onto the front of the brain case. It sticks out,” he said.
But these distinctions don’t always make it easy to decide what is a modern human and what isn’t. Take, for example, the 259,000-year-old fossil remains found at the Florisbad site in South Africa. This partial skull is among the examples that vie for the title “world’s oldest human remains,” but whether it’s truly human or proto-human depends on context we just don’t have, Potts said.
The skull is round, as you’d expect for a Homo sapiens, but it’s also thicker than our skulls typically are. For the most part it’s got characteristics that are clearly Homo sapiens, but it’s also got a few others you’d associate with older species. If we had a bunch of skulls from that site, we would have a clearer picture of what was going on, Potts said. We could see whether this was a group of particularly early Homo sapiens or one individual in a group of proto-humans who just happened to be a little more on the human side. But there’s just the one skull. So the scientists keep arguing about it.
Whoever the first baby was, somebody did take care of it. Evolutionarily, somebody had to, because modern human babies require more care, for longer periods of time (and probably by more people) than ancestral apes’ babies did. Three million years ago, those ancestors grew up much faster than we do today. Examination of layers of enamel in fossil teeth shows that early hominids were getting their first molar at age 3, twice as fast as us. Modern humans grow up more slowly because the development of our large, complex brain takes lots of energy, Potts said. “Brains are really expensive. We grow up slowly, and it takes a long time for that brain to mature.”
And as our species developed, so did the rituals and culture we placed around caring for babies — and losing them.
Just last week, the journal Nature published a paper documenting the oldest known human burial on the continent of Africa. Found under an overhang in a cave in Kenya, the grave pit contained the bones of a 2- or 3-year-old child who lived some 78,000 years old. Unambiguously Homo sapiens, the child was also unambiguously cared for. The positioning of the bones suggests that the body had been wrapped tightly in a shroud and laid on its side, its head on a pillow.
That kind of elaborate caring behavior and the whole concept of human babies existing are inextricably linked together. As brains got bigger, babies needed more, and their ever-larger-brained parents had more creativity to fulfill those needs. You’re never going to find a human baby with nonhuman parents. The change was too gradual for that. But the process of creating a fully human baby also created fully human caregivers.
“To that child’s mother and father, it was their baby,” White said. “And it died.”