)In the previous installment of my ongoing series on evolutionary biology questions, I shared my conversation with Mike Stell about original sin within the context of an evolutionary natural history. That topic leads naturally to a related question about who the original sinners were. Actually, both the blog commenter whose questions inspired this series and Mike Stell independently asked me very similar questions. What exactly does evolutionary biology say about the first humans?
Indeed, the story of the Fall is made even more implausible by scientific claims that the first human male and the first human female arose separately from large populations. I’ve never quite understood the claim that we should not conceive of a first male or female human because they arose in a large population. The odds of several female somethings giving birth to homo sapiens essentially simultaneously seems rather unlike IMHO. There had to be a first human male and a first human female, regardless of how many creatures were present when that took place.
To be honest, even as a biologist it took me a while to puzzle through these issues when I encountered them, partly because the answers are very counter-intuitive. It doesn’t help that popular imagination about evolution reinforces our intuition at the expense of what evolutionary biology actually says. The recent film X-Men: Apocalypse is just the latest example of a science fiction property that dips its toes in the waters of evolution but only serves to muddy them in the process. I wrote a more detailed x-amination of the film for BioLogos; one of the key difficulties is the way the film’s titular antagonist seems to blend evolution with a sort of Platonic idealism or essentialism.
It is common to hear that human beings evolved from apes. This is a convenient shorthand that is imprecise in ways that can create confusion. For starters, modern humans did not evolve from modern apes, rather both evolved from a common ancestor. Still, that common ancestor would probably seem to us very ape-like, so on that score the shorthand isn’t entirely misguided. But there’s a more subtle problem with both of these descriptions: species don’t evolve.
Dividing all organisms into distinct species is not straightforward. At any given moment, it may be possible to define boundaries. Looking back at the fossil record, which only offers snapshots of different points in history, drawing lines of demarcation seems natural. Ultimately, the idea that all species have sharp boundaries breaks down when trying to account for the taxonomy of every individual. One can no sooner set a minimum number of grains of sand that make a heap than draw species barriers between every living thing that has ever existed.
We might imagine an ideal or reference human and decide whether every organism is a human or not by how far they deviate from that ideal. If we make our assessment based on anatomy or on capabilities, we might find that infants or developing babies in the womb don’t come close enough. We can wait until adulthood to make our assessment, but then again we don’t wish to deny human dignity to amputees or those whose development was inhibited in some fashion. We can appeal to the genome, but then we are really splitting hairs if we say that one can be a human with 1,000 mutations but not 1,001. And that’s before we ask “mutations relative to what?” or account for the fact that 10,000 mutations of one sort could have no discernible effect, while 100 mutations of a different sort could have dramatic consequences.
Now just because species get fuzzy at their edges doesn’t mean they are a useless concept. There is no doubt that I am not a cuttlefish or a chimpanzee. A cow is never going to lay an egg from which a chicken then emerges. Turkey bacon will never be a perfect substitute for pork bacon. It’s just that species are categories we define after the fact, not entities unto themselves that can transform from one to another.
At the same time, the notion that there was a first Homo sapiens ultimately doesn’t work. If we followed humanity backwards in time, there would be no obvious place to draw a line between H. sapiens and earlier hominins. If we went all the way back to the common ancestor of humans and chimpanzees and then followed those individuals forward, what we would see would be two populations that stopped interbreeding and so eventually diverged enough that we would call one group chimps and the other humans. The population that eventually became human would never drop below about 10,000 individuals. We infer this from present day genetic diversity among humans; if the population size was substantially smaller than 10,000 we would see less diversity now. There wasn’t a single first human male or single first human female somewhere amongst this population; everyone in this population were ancestors to present day humans.
As to the bit in the original question about the first male and the first female arising separately, I believe this refers to the unhelpfully named “Y chromosomal Adam” and “Mitochondrial Eve.” These individuals aren’t the first human male and first human female. Rather, they are the most recent common ancestors of all men via patrilineal descent and of all women via matrilineal descent, respectively.
Men only get Y chromosomes from their fathers. Trace the son-to-father lineages back far enough and every living male line goes back to the same man; that’s Y chromosomal Adam. He wasn’t the only human male alive at the time, nor was he the only male ancestor of living humans who was alive at that time. Rather, any lineages from living people back to those other males have a female somewhere along the way.
Similarly, men and women only get their mitochondrial DNA from their mothers. Go back far enough up the son-and-daughter-to-mother lineages and you get to a single woman. She wasn’t the only human female, nor the only female ancestor. Any lineages from living people back to those other females have a male somewhere along the way.
This doesn’t necessarily mean that the Biblical couple Adam and Eve weren’t actual humans who lived at some point in history. They just couldn’t have been the only two humans, which is why I proposed an alternative way we could have inherited original sin from them.
As to the nature of that sin:
My point is that there isn’t any reason to think that the population from which humans arose was not violent as well. Indeed, there are violent species through all the phyla I know of, depending upon how one defines violence, so which one committed the first act of violence that could be called “sin”?
It’s not clear to me that the first sin was an act of violence. The event described in Genesis is not what we usually consider violence. Furthermore, when predators now act violently, we don’t consider that to be sin. Sin seems to be a combination of particular acts, including but not limited to certain forms of violence, and the knowledge that performing them is a rebellion against God. So the first sin was not the first time someone was violent, but the first time someone rebelled against God after God explicitly communicated which acts would be rebellious.
Next time we’ll look at whether an evolutionary perspective has anything positive to offer to make these challenges worthwhile.
Andy has worn many hats in his life. He knows this is a dreadfully clichéd notion, but since it is also literally true he uses it anyway. Among his current metaphorical hats: husband of one wife, father of two teenagers, reader of science fiction and science fact, enthusiast of contemporary symphonic music, and chief science officer. Previous metaphorical hats include: comp bio postdoc, molecular biology grad student, InterVarsity chapter president (that one came with a literal hat), music store clerk, house painter, and mosquito trapper. Among his more unique literal hats: British bobby, captain’s hats (of varying levels of authenticity) of several specific vessels, a deerstalker from 221B Baker St, and a railroad engineer’s cap. His monthly Science in Review is drawn from his weekly Science Corner posts — Wednesdays, 8am (Eastern) on the Emerging Scholars Network Blog. His book Faith across the Multiverse is available from Hendrickson.
This is where I am going to step in again and question the limits of Darwinian gradualism. “A cow is never going to lay an egg from which a chicken then emerges.” True, but it is possible that an ape-like creature had a child (or children) that was very different from itself. There is an ancient gene called SRGAP2 which has been duplicated 4 times in the human lineage (and not in any other animal). One of those duplications, SRGAP2C, has a dramatic effect on 1) overall brain size, 2) the number of connections in the brain, and 3) the plasticity of the brain. Interestingly, this duplication has been dated to just about the same time as the first fossils of the genus Homo. Could it be that this duplication arose in the germ cell line of one individual, so there were many gametes created with the same mutation, and thus many individuals with significantly larger brains and mental ability – in one generation? Or perhaps one individual arose with the mutation, who because of his superior intelligence became leader of the troop, and half of his offspring carried one copy of that mutation? And some of them mated and had a child carrying two copies? Since all modern humans have two copies, it is impossible to test whether there is a dose effect, but it seems likely that there would be one. It is tantalizing to think of the implications of that for an Adam, perhaps the first with two copies of SRGAP2, who would have been part of a larger population, yet significantly different from them – different enough to have a clear species demarcation in one generation, although the species would not have been totally separate until there were enough individuals with that difference who stopped breeding with their less intelligent former family.That new species would also be able to understand the ethical consequences of decisions, and thus able to decide to sin. Think about it.
Gerry,
Thanks so much for sharing this! It’s certainly a compelling scenario and you make a plausible case for it.
Certainly because of the way that development works, individual mutations can have dramatic effects. One could even imagine finding fossils of pre- and post-SRGAP2C and assigning them to a different species. At the same time, by other species criteria including the traditional interbreeding criteria one would have a hard time drawing a species barrier between individuals who only differed by that one gene, if you encountered those individuals in life. So while I think the challenge of defining species has connections to gradualism, a less gradualist understanding of evolution still faces some of those same challenges.
I will also admit that I’m making some assumptions about the general audience of this blog that may or may not be accurate in general, and wouldn’t apply to someone like yourself with experience in biology. I imagine most folks think of species in terms of what they see at the zoo — animals so obviously different in their shape and appearance that classification is nearly self-evident and intermediate forms are difficult to conceive of. As a result, I figure a scenario like what you describe is easier to conceive of and it’s the more subtle species distinctions and overlaps that need to be highlighted. Perhaps I overplayed that particular angle.
I should also add that my own background is in microbiology with a little dabbling in entomology. When I think of species distinctions, I think of my colleague who had to learn to differentiate 63 species of mosquitoes, sometimes by examining them under a microscope to tease out the subtle differences. And I think of bacteria and viruses, where the concept of a species almost seems irrelevant. That perspective on biology may bias me a bit towards a more gradualist view. In which case, I’m glad to have some balance from the realm of human biology.
Hi Andy,
Again, tardy but here goes. On the matter of sin, based upon Homo Sapiens appearing suddenly from multiple females who wee not H.S., then it could easily be the case that there were/are thousands if not millions of Homo Sapiens who never sinned. That’s a problem for the Bible but seems demanded by the model that you have proposed. Further, since in your post I don’t see any reason to think there was an original “Eve,” Paul makes no sense when he connects the common penalty for sin to one man, Adam, and the solution to one man, Jesus, in Romans 5.
Of course, the death aspect of sin is a problem in any case. Genesis records people dying after the rebellion recorded in Genesis 3 and Paul tells us that the penalty for sin is death. I do not think–and finally I can speak in an area I do have some expertise–that we can call this spiritual death only. In 1 Corinthians 15, Paul is concerned with physical death. The future resurrection of believers will be a triumph over death, which will have lost its sting. If physical death weren’t a problem and indeed a penalty, we wouldn’t need deliverance from it. To be clear, I am reading Romans 5 as saing, contrary to Augustine’s poor Greek skills, “and death passed to all men because all sinned.
However, from an evolutionary point of view, death is not only not a problem but part of the system that God established. The reference in Genesis 3 to the Tree of Life does not solve this because if there was not a first human pair placed by God in a garden, there wasn’t a tree of life,or of the knowledge of good and evil or anything else because those humans did not ever exist. Now if some humans have never sinned, and death is the penalty for sin, why do all humans die? The implication to me is that all humans are stuck with death because God designed death and it is not a penalty for sinning. It is part of the system. Exegetically I cannot see any way to put the biblical proclamation and the scientific assertions together.
Regarding the common descent of all humans, I’m still lost. The first male Homo Sapien is born at one point among one population. The first female Homo Sapien is born thousands of miles and thousands of years apart. How does this make for common descent for humans from both. I’m not following your explanation. Why would we ever expect that two different populations in different places and times would each give rise to and maintain the Homo Sapien mutation?
I’m no expert in biology certainly but what you seem to be saying is this:
Given a population of at least 10,000 somethings, the mutation(s) required for a Homo Sapien happened numerous times separately from numerous mothers.
Since we cannot clearly distinguish between a Homo Sapien and its parents, we cannot even say that female creature A gave birth to a Homo Sapien.
For the sake of argument, I will grant, though I have no good reason to do so, that the Homo Sapien mutation is very close to its immediate parent. Why does this mutation or combination of mutations get passed on to offspring? That is to say, mutations are the exception for any given species, not the rule. Otherwise, wouldn’t the number of mosquito species be closer to Avogadro’s number? There is no reason to think that the Homo Sapien mutation would happen again at all. The first Homo Sapien male in a population has to reach a certain age to have any opportunity of producing offspings. That these will be Homo Sapien offspring without a Homo Sapien mother seems to assume a lot.
Further, if that Homo Sapien is truly distinctive, more intelligent for example, I could easily see other members of the population rejecting him/her because they are so different. If the difference between this human and its ancestors is, on the other hand, small, why don’t they still exist? There had to be a lot of them. As to the cow laying an egg, humans would seem to me to be quite different than any other living thing. I’m not aware of any apes that have multiple languages with distinct vocabularies and grammar, with thousands of words in each language. I’m not aware of any creature but humans creating buildings, welding metal, riding bicycles, inventing math concepts to inflict upon children in school, etc.
I may have my biology wrong, but this is the direction that I am thinking. I don’t see how we can accept the Bible’s claim about death being a penalty for sin when everything “by design???” dies. I don’t see why we should expect the human mutation to be replicated. Of course the last tie I heard about genetics it was in a physical anthropology class in the 1970’s.
Finally, I have to come back again to the issue of, Why implicate God? As a Christian, I affirm that the biblical God exists and acts. Yet, week after week I hear atheists proclaim that we can explain everything about the origins and development of all living things through science and anything we cannot explain, we just need more time to research. That sounds like the biblical authors, being ignorant, thought that a supernatural being was needed to explain some aspects of the material world but now we know better. I can’t understand why any scientist with a Christian worldview would not be pushed to this conclusion.
Oh, and I want to pose another question to you that is related to this last paragraph and relates to something that you said perhaps in passing. The whole evolutionary biology model assumes as a fundamental rule, so far as I can see, that given enough time, all things not only can happen but a vast number of highly improbable things will happen. Statistics is not my specialty either, but I imagine that it would be possible for someone to analyze the likelihood that I will be struck by lightening while eating an ice cream cone in the local park. I’m guessing the odds of this happening are very very small. The fact that it is possible does not mean that we should expect it to happen. I can spin two roulette tables for centuries and never have both of them simultaneously have a ball fall on the same number..
The mere fact that it is possible given enough time is far from guaranteeing or even suggesting that it will.
In my limited knowledge of biochemistry, don’t an awful lot of statistical improbabilities have to take place, like formation of particular amino acids, proteins lining up in very specific ways and more amount to going to Las Vegas and winning one million Blackjack games in a row? I’ve read numbes that actually makes that sound far more likely than many biological events that had to take place. Why is time alone a basis for asserting hat they did all do so randomly?
Ken