Who Was The First Person?

That was the question my son asked, from the back seat of my wife’s car. I don’t remember the context, but I think we were talking about his grandparents. Things my dad had done, things my wife’s father had done, sharing family stories. That sort of thing. And then he asked it. “Who was the first person?”

That is a hard, heavy question.

What is a “person”?

Merriam-Webster gives multiple definitions for the word “person”:

  1. human, individual —sometimes used in combination especially by those who prefer to avoid man in compounds applicable to both sexes <chairperson> <spokesperson>
  2. a character or part in or as if in a play : guise
  3. a : one of the three modes of being in the Trinitarian Godhead as understood by Christians; b : the unitary personality of Christ that unites the divine and human natures
  4. a archaic : bodily appearance; b : the body of a human being; also : the body and clothing <unlawful search of the person>
  5. the personality of a human being : self
  6. one (as a human being, a partnership, or a corporation) that is recognized by law as the subject of rights and duties
  7. reference of a segment of discourse to the speaker, to one spoken to, or to one spoken of as indicated by means of certain pronouns or in many languages by verb inflection

For these purposes, we’ll focus on the first definition: “human, individual”. Which shouldn’t be a surprise, as it’s pretty clear from the context that my son’s question should be understood as “who was the first human”.

Human beings are formally known Homo sapiens, with contemporary human beings classified in the subspecies Homo sapiens sapiens – a rather arrogant sounding name, since it means “Wise wise man” when translated from Latin. We are part of family Hominidae (also known as “great apes”), a family that includes Homo (us), Pongo (orangutans), Gorilla (gorillas, go figure), and Pan (chimpanzees). Hominidae is part of the Primates, which is an order of the class Mammalia. At present we are, arguably, the most successful branch of both Primates and Hominidae, as we have a globe-spanning range of habitation. We’re certainly the most successful current branch of Homo, as we’re the only extant branch of that genus.

primate-cladogram-2_med

Our family tree

So, who was the first Homo sapiens?

This is where things get tricky, because “species” is a difficult concept to pin down. You’re probably familiar with some version of Mayr’s Biological Species Concept, which defines a species as “groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups”. The problem with this definition, and this is a problem biologists are well aware of, is that nature is “squishy”. Not all species reproduce sexually, for instance. Does that mean they aren’t a species because this concept doesn’t apply? If two different species can successfully breed, even if they wouldn’t normally do so in the wild, does that make them different speices because they’re usually reproductively isolated or does it make them the same species because they can still produce viable offspring? The answer is the subject of a lot of arguments among biologists.

This “squishiness” combines with evolution to make it impossible to pin down a “first” Homo sapiens, or even to say for certain what was H. sapiens and what was a different Homo species. The Neanderthals, for instance, were Homo neanderthalensis, a different species from Homo sapiens, but there is enough genetic evidence to make an argument that they certainly weren’t reproductively isolated from our species. The jury is still out on that, but given some of the other things humans will do today it’s certainly not unreasonable to assume that our ancient ancestors were open to having sex with another species of Homo.

All we can say for certain is that our species differentiated itself from our direct ancestor species – Homo erectus (“upright man” – somewhere between 1.8 million years ago and 200,000 years ago. Which means that we likely overlapped with H. erectus for a significant amount of time, as the oldest fossils of H. erectus are around 1.9 million years old and the youngest are around 70,000 years old. So, worst case, we overlapped with H. erectus by some 130,000 years, which is significantly longer than recorded human history. But we can certainly speculate. There wouldn’t have been a sharp dividing line between H. erectus and H. sapiens, and certainly no moment where a H. erectus mother looked at her baby and said something like “hey, this is different“, because evolution doesn’t work like that.

The lineage that gave rise to H. sapiens would likely just have started off as just another subspecies of H. erectus, like H. erectus erectus (“Java man”), H. erectus nankinensis (“Nanjinj man”) or H. erectus georgicus. That subspecies would have been somewhat geographically and/or culturally isolated from its neighbors – although possibly still indulging in the occasional opportunistic “gene swapping opportunity” – until, over time, it became different enough that it became a distinct organism. Could the new archaic H. sapiens have successfully interbred with H. erectus at that point? Possibly. We could have interbred with H. neanderthalensis, after all. But since all we have left of H. erectus is fossil bones, we’ll probably never know for sure.

That said, genetic studies have indicated that there is something approximating a “first” human man and a “first” human woman.

It’s fun to stay at the MRCA!

MRCA is the Most Recent Common Ancestor, and it’s exactly what it sounds like: the most recent individual from which all members of a set group are descended. For you and your siblings (if you have any), your MRCA is your father and mother. For you and all of your cousins on your mother’s side of the family, your MRCA is your maternal grandparents. And so on. Generally speaking, the larger the group the further back you have to go to get a MRCA. Also, the paternal and maternal MRCA need not always have lived at the same time. Imagine yourself as having a half-brother because one of your parents divorced and remarried. YOu might share a father with the half-brother, making your father the paternal MRCA for that group. But you might have to go back dozens of generations to find a maternal MRCA.

The maternal MRCA for all of H. sapiens is nicknamed the Mitochondrial Eve, and she lived in Africa quite some time ago. How long? well, depending on the type of analysis applied, it could be as long ago as 234,000 years ago or as recently as 99,000 years ago. I won’t pretend to understand the details of how that was calculated, beyond the simple statement that it has to do with mutation rates in mitochondrial DNA – the DNA of the little organelles that our cells use to convert oxygen and sugar into energy. I’m a stockbroker, after all. Not a geneticist or cell biologist.

Our paternal MRCA has been nicknames the Y-chromosomal Adam, and is currently estimated to have lived around 200,000 years ago. Also in Africa, so there is a slim possibility that our paternal and maternal MRCAs knew each other. Don’t count on it, though.

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