*chuckles* I used the word apotheosis!

Just the other day, I was feverishly studying for my last exam of the year at some unfortunately late hour of the night. A thought came to me that wasn't necessarily very original, but it seemed quite clever at the time. I tore off a corner of the page I was writing on, scrawled an illegible and large unintelligible note, and went back to studying.

So now, I present to you the thoughts that occur to me late at night. It's a divergence from the subjects of the last few months... which most of you probably welcome.

I've been thinking about litter size. More specifically, human litter size.

Wait for it... trust me, it's worth it. At least for the laughs.

Why do humans have small litter sizes? Until fertility drugs, women would give at birth to two or three children at once only rarely. Total family size tops out at a dozen or so, right? As I'm sure you're aware, this is exceedingly rare, even for relatively 'advanced' species on the evolutionary tree. Most species have lots of offspring in lots of batches. Only a few of the larger (and more evolved) species have such a small number of offspring.

Well, all of my readers are currently wondering if I ever took a basic biology course. Or even watched 'Wild America' on the television when I was six. Trust me, I did both.

The classical answer is that humans invest a lot more in their offspring than most other animals. We pour huge amounts of work into keeping them alive (and nutrients, and time, etc.), whereas less evolved animals have a thousand offpsring in the hope that a handful get to reproduce themselves, right? Makes sense, at least on a surface level.

But here's the interesting part:

An underappreciated effect of having large litter size is that it provides for a large amount of genetic diversity in offspring, right? Recombine the genes enough way, and you'll get a handful of offspring per generation that are exceptional, and have that tiny bit of selective advantage that moves them toward. This is further enhanced by the general rule that DNA repair/fidelity mechanisms are much better in more highly evolved species... which, while being good for individual survival, is not necessarily very good for species-level genetic diversity.

So what does this mean? It means that as evolution progresses, the shift focuses more and more towards preservation of individuals of the species. This selection works spendidly for producing humans, right?

Yet there are side effects to this. Focusing on individual survival short-circuits evolution. Species-level genetic diversity decreases significantly, as do the number of possible permutations per parent. Heck, we talk about 'overpopulation' of humans at some 7 billion, right? Yet less developed species have orders of magnitude higher numbers, and a consequently higher genetic diversity.

What I think this means is that evolution is self-limiting. It is an asymptotic process; originally, very important as a driving force in creating diversity, but eventually defeating itself when it reaches a certain point. One could even argue that human intelligence (in particular medicine and civil engineering) has removed many of the selective pressures that were still being exerted on us as a species.

Are we nearing our biological apotheosis?

I wonder... has this pattern repeated itself in the past? Has a dominant species that stopped evolving been swept away in a cataclysm to be replaced by nimbler, more 'evolvable' species? I don't know if the dinosaurs (or other similar extinctions) count as this, but it is an interesting thought.

I suppose it almost sounds like hubris, but I think it only makes sense. Maybe it will take another few million years, but I think evolution has stopped at humans for logical reasons, not our self-centeredness.

Now is my readers' chance to explain to me that this thought has been elaborated in depth (even mathematically!) by some renowned evolutionary biologist. But I felt good having an original thought for once, instead of spitting back facts to a soulless exam paper.

I'd also be interested to hear more points supporting my idea, beyond DNA replication fidelity, litter size, and intelligence. I think it all comes down to valuing individual rather than species-level well-being.