Let's have another post, shall we?
It's not even next week.
It's been reported in The Guardian that Steve Jones is claiming that humans have reached their evolutionary zenith (We're as good as we can get, says evolution expert). In the past, I've wondered about human evolution in that ailments which would still have been fatal until fairly recent times in human history can now be cured. But that is without, say, modifying a person's genetic structure to allow them to pass on an inherent immunity to their offspring. That person survives, but has no genetic advantages to offer future generations. However, I find it unethical to subscribe to Nature's callous and brutal indifference to humanity even although I understand that natural selection is a part of existence.
But it's not just humans either. Think of the species of domesticated animals which we've genetically engineered to yield better and increased amounts of meat, wool, milk etc. When the animal falls sick we either summon the vet or take the creature to it. Have domesticated animals also ceased to evolve in response to natural conditions?
I know some of the commenters have wondered why women aren't getting much airtime, but that's because, I believe, when it comes to birth defects, the quality of sperm of older men is more likely to be the source of birth defects. I'm not sure whether women's eggs are subject to the same decline in quality because they're born with a finite number. Unlike sperm, ova are not being progressively made. Bottom line: I'm past a safe age for fathering children.
I also assume that "In the west, men are becoming fathers later and there are fewer older fathers, which means a sharp drop in the number of genetic mutations possible" means that the average age of fatherhood has risen and that fewer middle-aged men are fathering children. The sentence is a little confusing. Similarly
is also a little confusing, but I guess means the mean age. In other words, if you're between 29 and 35, you are most likely to become a father, and after that not likely at all. Once upon a time, the range would've been much greater.
For a time, it seems, genetic variation in the West might come from a combination of different races fusing together – to our advantage, perhaps. Whether that means that countries with a very limited racial mix are looking at the exacerbation of negative factors in their genetic make-up I can't say. I suspect that in a sufficiently large population, this probably isn't going to be a serious issue.
But it's not just humans either. Think of the species of domesticated animals which we've genetically engineered to yield better and increased amounts of meat, wool, milk etc. When the animal falls sick we either summon the vet or take the creature to it. Have domesticated animals also ceased to evolve in response to natural conditions?
I know some of the commenters have wondered why women aren't getting much airtime, but that's because, I believe, when it comes to birth defects, the quality of sperm of older men is more likely to be the source of birth defects. I'm not sure whether women's eggs are subject to the same decline in quality because they're born with a finite number. Unlike sperm, ova are not being progressively made. Bottom line: I'm past a safe age for fathering children.
I also assume that "In the west, men are becoming fathers later and there are fewer older fathers, which means a sharp drop in the number of genetic mutations possible" means that the average age of fatherhood has risen and that fewer middle-aged men are fathering children. The sentence is a little confusing. Similarly
"Perhaps surprisingly, the age of reproduction has gone down – the mean age of male reproduction means that most conceive no children after the age of 35. Fewer older fathers means that, if anything, mutation is going down."
is also a little confusing, but I guess means the mean age. In other words, if you're between 29 and 35, you are most likely to become a father, and after that not likely at all. Once upon a time, the range would've been much greater.
For a time, it seems, genetic variation in the West might come from a combination of different races fusing together – to our advantage, perhaps. Whether that means that countries with a very limited racial mix are looking at the exacerbation of negative factors in their genetic make-up I can't say. I suspect that in a sufficiently large population, this probably isn't going to be a serious issue.
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