Interesting read (registration probably required) by Jim Baen, from the Robert J Sawyer mailing list.
We’ve long had the arguments that evolution does not really act on anything that happens after child-bearing age. By that point, whether an organism would survive to reproduce had been determined, and no matter how severe the problems (or how impressive the survival), the genes would have already been passed on. Huntington’s disease, for example, is one of the few diseases that’s controlled by a dominant allele. That is, you only need one copy of the disease allele to get the disease, and there are no carrier. Generally, dominant genetic diseases are very rare because there’s a lot of evolutionary selection against them; but since Huntington’s doesn’t strike until after the person has had a chance to have children and pass it on, that selection pressure isn’t there. Likewise, there isn’t a lot of benefit to living for 200 years if you can only have children into your 40’s, or if you get eaten or sick so long before your parts wear out.
Of course, that’s all in the past, some say, and the future may hold nothing but longer lifespans for humans. After all, with technology we can live much longer, achieve much more, build more wealth. With our society we can improve the lives of our children and their children, or even use frozen tissue or other fertility treatments to extend our reproductive years… if only we could keep our minds intact long enough for it to matter.
The interesting question is: maybe dying has some evolutionary advantage?
Extreme polygamy = bad (essentially reducing your gene pool since only a few males mate, increasing recessive traits). Older successful males are more likely to be polygamous in culture, so it’s possibly that death acts as a mechanism to stop the unbounded accumulation of wealth and mates by any one person — and the accumulation of recessive desease genes in their offspring. Violence may also be an issue in this hypothetical model: once you get one person with such a monopoly on mates, there will be a lot of pressure for others to try to take that (whether challenging to take it wholly, or sneaking a few mates away here and there).
Also, what about the higher order effects? Shorter generation times lead to more responsive evolution (that is, better genomic response to change). Of course, for that to work really well generally requires large “litters” with a large number of acceptable losses in each generation. As mammals, we tend to follow a different strategy where we have a small number of children and nuture them to maximum fitness. Plus, as humans we use culture and technology to adapt, and genes that help us accrue more knowledge and design better tools for a longer period of our life seem like they would be beneficial. Very beneficial. On the other side of the coin though, is the saying that “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” If we don’t have people getting old and dying off to change our customs and beliefs, then that sort of toolmaking culture fails us as a mechanism of adaptation.
There was an interesting idea presented in Permanence (Karl Schroeder): technological/cultural adaptation is a very expensive way for a species to live. It allows for adaptation to a lot of environments, but always sub-optimally. A crocodile in a swamp, for instance, lives its life swimming and eating. A human attempting to live in the same environment would need a spear gun or net of some kind to catch food, a boat, and to get to the bottom some scuba gear, a few swim fins, and a wetsuit to keep warm. That’s a costly way to live, and while it may perform better than the crocodile in the short term, and work great if most of your existence is spent away from the swamp and you only really vacation there, it’s not really a way to live in a swamp on the scale of thousands or millions of years. All it would take is for some of that knowledge to be lost (how to fill an air tank, or how to sharpen a spear) and the survival ability goes way down.
Look at crocodiles. Humans might move into their environment—underwater in swamps. We might devise all kinds of sophisticated devices to help us live there, or artificially keep the swamp drained. But do you really think that, over thousands or millions of years, there won’t be political uprisings? System failures? Religious wars? Mad bombers? The instant something perturbs the social systems that’s needed to support the technology, the crocodiles will take over again, because all they have to do to survive
is swim and eat.
Permanence considers the decline of the million-year civilization. The thing about civilization, mass production and technology is that we can rely on the brilliance of a few to carry the rest of us, so we lose all selection pressure for brains. Eventually, no one can repair techological devices, or improve or alter a use to meet the needs of a new situation. In a society of users, when something eventually breaks, we all go extinct. This sort of idea is also present in Idiocracy as well, where a technological society, which cushions us from the realities of natural selection, no longer selects for the intelligent people that can maintain that society. Evolution by natural selection is based on a tautology:
“that which survives, survives”, as Douglas Adams put it. But it’s a profound tautology nonetheless. If, as in Idiocracy, people who are less intelligent breed more (much more) than others, then the human race will be brought towards that, the subtype which most sucessfully takes advantage of its environment.
What we found instead was that even though a species might remain starfaring for millions of years, consciousness does not seem to be required for toolmaking. In fact, consciousness appears to be a phase… We know now that [consiousness] evolves to enable a species to deal with unforeseen situations. By definition, anything we’ve mastered becomes instinctive. Walking is not something we have to consciously think about, right? Well, what about physics, chemistry, social engineering? If we have to think about them, we haven’t mastered them—they are still troublesome to us. A species that succeeds in really mastering something like physics has no more need to be conscious of it. Quantum mechanics becomes an instinct, the way ballistics already is for us. Originally, we must have had to put a lot of thought into throwing things like rocks or spears. We eventually evolved to be able to throw without thinking—and that is a sign of things to come. Some day, we’ll become… able to maintain a technological infrastructure without needing to
think about it. Without need to think, at all…
With a longer-lived species, despite the problems discussed earlier, we might be able to avert these sorts of problems. However, we would need to be immortal to continually look after our progeny through the eons. But eventually, of course, death in one of her many guises will find you. So the answer may be picking up and moving for greener pastures, no matter how long lived the species. As long as this happened often enough, we would likely not fall towards “direct adaptation” mechanisms, but maintain a technological adaptation. It’s only through constant challenges to survive, succeed, and breed that intelligence, consciousness and cultural adaption will be preserved in the species.
In fact, we may find that selection for a longer-lived species goes hand-in-hand with selection for intelligence in a technological society: it takes so long to learn what you need to survive and thrive (I’m 27 and still in school for years to come yet!), that only long-lived (and late-breeding) members are sucessful.
On the other hand, there may be another case where shorter generations may have a (meta)evolutionary advantage. It’s only as long as we’re willing to take risks and go to test the limits of our intelligence and ability to survive that we feel any kind of selection pressure, and when the phrase “you’ve got your whole life ahead of you” means so much more, risk aversion may become the norm. Also, with intelligence and consciousness comes senescence, dementia, and insanity. It’s possible that the chances of falling prey to these increase with age (unless a stable brain is selected for and has a chance to evolve).
“We live in a society exquisitely dependent on science and technology,
in which hardly anyone knows anything about science and technology.”