I’m enjoying a rare opportunity to indulge in a little bit of curation. At Carnegie Museum of Natural History, we are putting up a new display on human evolution called Becoming Human and I’m working with our wonderful exhibitions team to work through the various stages of its development. It’s going to be installed next February in our Pleistocene gallery, alongside some impressive mounted skeletons of large animals of the period.
The exhibit will be modest, maybe about 8 feet long, not far from the Irish Elk. It will feature replicas of roughly nine skulls of early hominids up to modern Homo sapiens sapiens, grouped taxonomically, along a timeline representing the latest scientific evidence.
This is an important addition to our overall exhibition offer. For on thing, it describes the evolution of human beings, a story which is not currently anywhere in our halls. Adding in this information helps place humanity within the evolutionary tree in an unbroken (though punctuated) trajectory from the beginning of the life on earth. For an institution like ours, that has representative organisms going back that far, this is important.
Including human origins in also puts the evolution of human culture in time and place. Modern humans evolved with the Earth was very different from today, in a rapidly cooling climate and a global ice age. Ice caps created connections between continents that allowed our ancestors to spread. But when did humans transition from being essentially intelligent primates to something we could meet with self-recognition?
Scientific evidence points to the physical and behavioral traits shared by all people originating from apelike ancestors and evolving over a period of approximately six million years, during the Miocene. Molecular evidence suggests that between 8 and 4 million years ago, during the late Miocene/early Pliocene, first the gorillas, and then the chimpanzees (genus Pan) split off from the line leading to the humans.
But the transition to humans is a lot more than simply walking upright. We have a very popular hall of Ancient Egypt, and even our oldest artifacts from the region (ceramic vessels, roughly 5,000 years old) represent a huge intellectual and technological leap from what has happening at the beginning of the Holocene, 12,000 years ago. Was it a gradual change over this period or was there a single giant step to another cultural state? Perhaps both are right. Unfortunately, very few Upper Paleolithic tools have so far been recovered from Egypt, making this analysis difficult.
But even answering this question wouldn’t get at a deeper question – what is it really to be human and can we look at a set of skulls and ascertain that? Are we just monkeys who can play backgammon? Are we doing exactly than our biological legacy suggests or are we something fundamentally different? That is a question that has kept one or two philosophers awake at night over the couple of centuries since Charles Darwin and his predecessors.
One fallacy about that question, to my mind, is its inherent bias. While of course we are best at being human, and intellect plays an important part in that, intellect, that is to say humanity, is the yardstick by which society measures the worth all other animals. Is that fair? We aren’t as good as a seahorse at picking brine shrimp out of the water column, or preening our relatives as a macaque. In fact our eye-hand coordination doesn’t even come close to a chimpanzee’s. Even if we scale it back a notch and ask whether humans are the only animals with self-awareness, it remains problematic. Is your golden retriever aware of its own existence when it steals a piece of pizza off the coffee table and then tries to hide it from you? Perhaps not consciously (although that’s debatable) but it definitely knows the difference between you and itself in a hierarchy and can anticipate consequences of its actions. In fact, Darwin ran series of experiments intended to demonstrate the intelligence of earthworms.
Whatever the secret sauce is that makes us human, according to researchers into Neolithic peoples, that ‘x-factor’ seems to have arisen roughly 9000 BCE when polished stone tools were developed and the last ice age ended, despite humans being anatomically indistinguishable from modern humans for 200,000 to 300,000 years. Then, when agriculture did develop, it appears to have emerged independently and spread from places as far-flung as Mesopotamia, China, South America and sub-Saharan Africa.
And what about the future? One of the main conversations we’re having now at the Carnegie concerns the Anthropocene, or Age of Humanity, acknowledging the impact our species is having on the geological record of the future. The impacts of people are changing the ecology of the planet and, by extension, the context in which Homo sapiens sapiens of the future will be evolving. If global warming at the end of the Pleistocene epoch sparked the rise of agriculture and culturally modern humans, what effect might global warming in the Anthropocene have?
Modern humans have evolved from our distant primate ancestors in a process called “neoteny,” or retaining the characteristics of youth into future generations. A good example of this is the axolotl salamander, which lives to reproductive adulthood in a larval state. (In fact, they retain the ability to undergo metamorphosis into something like a tiger salamander following exposure to thyroid hormone – though don’t try this at home.) Compared to our ancestors, we have less body hair, larger eyes and heads, not unlike the babies of many primates. If we continue to evolve, will we continue along the same course? The artist’s rendition below suggests we might end up looking a little like the Gray People of Roswell fame: larger head and eyes, lower muscle mass, that is even more like out-sized children than we do now.
Of course, nobody knows the answer to this, but given how different our ancient ancestors look to us, it seems that anything is possible. (I tried to find a review article on this topic, but the literature is so vast, I gave up in frustration). That’s a deep dive for another post. But for now, I’ll leave you with one final thought:
Humans evolved, in part, in response to the challenges and opportunities presented in the environment. In a future dominated by human influence, what will those options be like – dystopian? In harmony with nature? Many or few people? With our without icecaps and coral reefs? We can’t know. But we do have a choice of what today’s inputs will be to that distant time. And the I’m certain that a future we design intentionally, with the application of sound science, will be better than one that is the result of random, unthinking action.
Cover image: A reconstruction of the head of an Australopithecus afarensis on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. Licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.