More on the topic of concealed ovulation in humans

There was an entry in this blog a few weeks about what seemed to me to be a puzzle, namely, how can we understand “concealed ovulation” in humans from the perspective of evolutionary biology. I recently happened upon the book “The Third Chimpanzee” by evolutionary biologist Jared Diamond. He writes, on page 78 of my paperback copy, that “…the most hotly debated problem in the evolution of human reproduction is to explain why we ended up with concealed ovulation….”.

I suppose I must admit I found it gratifying that at least I wasn’t being a dunderhead in writing about this puzzle. That is, if distinguished professional biologists cannot agree on the reason for this trait, then a layman in the area (such as myself) certainly has the right to be puzzled by it.

At any rate, Diamond goes on to say that there are at least six current theories about why the trait evolved. As I understand his more lengthy explanations, it evolved for one of the following reasons:
1. To enhance cooperation among males (he considers this one to be rather male chauvinist for some reason)
2. To cement the bonds between mates
3. To enhance the probability of the female to receive her fair portion of meat from male hunters
4. To force the male into a permanent marriage bond (he considers this one to be “gender neutral” in a gender politics context)
5. To encourage seevral males to help her, and to at least not kill the infant (this one, by Sarah Hrdy, he applauds as a welcome “feminist” perspective)
6. Because a woman that had a tendency to conceal ovulation could not avoid the risk and pain of childbirth, and hence left more descendants that did those that did not conceal it (this is the theory that Nancy Burly suggested in about 1979, and the one that I mentioned as being a common sense explanation in my earlier post).

I find it rather regrettable that Diamond seems to place so much emphasis on being politically correct. For example, he approves of number 5 because it “overturns masculine sexism and transfers sexual power to women”. This seems an odd reason to like a hypothesis, for shouldn’t scientific truth be the only guide for favoring an explanation of any natural phenomena? Nevertheless, the several pages he devotes to this issue involve some intriguing speculation, and I find it quite interesting.

The Evolutionary Puzzle of Concealed Ovulation

Comments on The Accidental Mind, by David J. Linden

I am fascinated by this excellent book. It deals with how the brain, especially the mind, has evolved, and emphasizes that the brain is not an efficiently designed gizmo. Rather, he arguer that it is a serendipitous kludge put together willy-nilly through many diverse evolutionary steps, with many subsystems inefficiently built on top of each other. It is a tightly argued book, and makes good cases for explaining how brain evolution gives rise to a wide range of human behaviors and emotions (love, memory, dreams, and God, as stated on the cover).
However, one argument he makes leaves me puzzled. He discusses, on page 149, the question “why do humans have concealed ovulation and recreational sex?”. This is, seemingly, two different questions, is it not? The first part, about concealed ovulation, is very interesting to speculate on from the perspective of evolution. The second part of the question though seems to me to be not a weighty one. For isn’t the obvious answer that it is fun and feels good? Don’t all animals, in a sense, engage in recreational sex? No animal, as far as I can tell, does it because it is intentionally going about the business of procreating. Now, that of course is the effect of it, and in fact why nature has made it feel good. If it didn’t, an animal would be disinclined to perform the act, and its genes would not be in the gene pool. So it seems to me. I am a simple layman in this area, so I could be way off base here, and maybe not fully understanding some subtlety in the question.
Let me turn to the first part of the question, that about concealed ovulation. He presents a hypothesis to answer this, attributed to Noonan and Alexander of the University of Michigan. This hypothesis is that concealed ovulation evolved as a means of keeping the male around. Reasonable sounding, as one can see that from a game theory perspective that if ovulation were evident to a male, he might leave upon having sex with an ovulating female to have impregnate another female. Since he is not sure, and he doesn’t want to take a chance that any offspring that the first women has are in fact from another male, he sticks around. He does not want to waste resources raising another males offspring (which would not propagate his genes). Presumably, a male sticking around does, according to this explanation, tend to increase the chances of the woman’s offspring surviving and passing on her genes. Amusing if this is true: maybe this is an indication that we males are good for something after all.
We must quickly add though that male usefulness may not follow as being true today. A protective male could have been much more useful in prehistoric times to provide protection against invaders, predators, and other violent enemies.
But it is not so clear to me that this hypothesis makes sense from a “selfish gene” point of view (the Richard Dawkins book of that name makes perfect sense to me, so I look at everything about evolution from that perspective). It seems to involve assuming that a given male consciously wants to maximize his genes representation in the gene pool, doesn’t it? And as I said above, it seems to me that all animals, including humans, engage in sexual activity because of the pleasure it brings. Putting ones genes into the gene pool, i.e., procreating, is a byproduct from the animal’s point of view.
The other thing that bothers me is that this Noonan-Alexander hypothesis only seems to explain why ovulation is hidden from the male. It is not clear that it explains why it is hidden from the female as well, who will have, presumably, a more nuanced sense of what her body is doing that an external male would have.
Why, I wonder, do people not consider what seems to me to be a more simple explanation of concealed ovulation? Namely this: humans have gradually evolved conceptual knowledge of consequences, or “cause and effect”, and must have long ago (in prehistoric times) figured out that the sex act could result in babies. Perhaps, once a woman knew that to be the case, she would be more inclined to abstain from sex when she was aware that she was ovulating. If she did abstain, she would be able to enjoy all the “recreational sex” she wanted, but she would less likely to be impregnated. To be sure, there have no doubt been times when a woman wanted to have children, but it is easy to imagine that babies could have been a severe burden at many times in human history. Hence, on this view, the woman that somehow mutated a tendency to conceal the fertile times could give rise to more offspring than would a woman that avoided sex when she knew she was ovulating. The latter type of woman would be gradually supplanted in the gene pool, and women with concealed ovulation would thrive.
I seem to recall that in one of the many books I have read on “evolutionary biology” that this theory of mine has been considered by others and soundly rejected. If anyone can enlighten me as to exactly why it is faulty, I would be most grateful.
Note: There is a wikipedia entry on "concealed ovulation", but it does not discuss why it evolved. It does point out that some other mammals, such as rhesus monkeys, have it.