A few years ago I was talking with a staff member of a local pet shop. She was telling me that bulldogs can no longer have litters in the natural way. They have to be artificially inseminated and give birth by caesarean section iirc. This got me to thinking. With all the humans being given fertility drugs and conceiving by in vitro fertilization, are humans headed someday for mass infertility? Will ALL humans someday have to take fertility drugs or conceive by in-vitro fertilization, with all the people doing that now?
I realize that there is a movie now that may bring up this very point. Someone please provide a link about this movie, if applicable. But realize it wasn’t this movie that inspired me to submit this post, if this movie somehow applies.
The declining quantity and quality of humanity’s sperm was first introduced to me in a thread about the decreasing teenage pregnancy rate. I found it amusing because the left was arguing that teens were increasingly using condoms and birth control pills whereas the right were touting their faith based abstinence programs and, to me, the idea of a researcher interjecting and basically saying “Nope! Our sons and daughters are still having orgies without protection, but our sons are shooting blanks more or less, so less babies!”
So I guess it’s a crisis? They give various hypotheses to explain the observed decline, like chemicals, pollution, hormones, etc. From where I’m sitting it doesn’t seem like a serious problem since the human global population doesn’t seem to have any difficulty whatsoever growing by leaps and bound. Maybe all this industrial waste in the air and water will turn out to have a good side.
We have threads like this quite often, and they are based on a misunderstanding of how evolution works. Firstly, the number of people conceiving thru IVF is tiny. Really tiny. Even if you include only people in First World countries, it’s tiny. Secondly, even if we assume that all of those receiving those treatments do so due to genetic problems, their children do not subtract from the number of children born w/o IVF. So, there may be more of the “bad” genes getting into the population, but there are still more “good” genes getting in. Finally, and most importantly, those “bad” genes aren’t conferring any advantage in the reproductive success of people born thru IVF.
It’s possible that a trait which neither confers an advantage nor a hinderance to the reproductive success of the offspring can become fixed in the population thru genetic drift. But we’d be talking a very long time (hundreds, thousands of generations), and the IVF method would have to be readily available to every human in the world. Even in First World countries, it’s still not a viable option, economically, for many (most?) people. With a species as large as ours, that’s just not likely to happen.
If our species becomes infertile, it’ll more likely be due to some environmental damage, and then we won’t be only species affected. It’ll most likely be part of a much larger, calamitous event.
This is a very eurocentric concern. Are europeans, americans and (add other industrialized countries here) headed for infertility. Maybe. Is there an 80% of humanity ready to take their place were they to fail to perpetuate themselves, sure thing.
I wonder how (or if) this might tie in with the phenomenon of dropping birthrates in developed nations (to which Sapo alluded). Why do birthrates drop in developed nations? Is it because people choose to have fewer babies, or is there something about living in a wealthy nation that might lower sperm count, or is it some combination of both?
I wonder if there is a breakdown of sperm count by nation.
In a rural economy, more kids means more workers. In a developed country, more kids means more mouths to feed. It’s more of a choice than anything else. Subgroups in developed countries (eg, Mormons, or Catholics until recently) seem to do just fine having big families.
Good point about the workers…and not only do people in developed countries not need large families, but they have much better access to reliable birth control. There are also incentives to have smaller families, such as opportunities for women to work outside the home in professional jobs, and more money to go around when there are fewer children.
The reason Bulldogs give birth that way is because they have been so bred for large heads and small hips that their pelvises are no longer large enough to pass the humungous heads very easily.
The reason people are having reduced birth rates in developed countries is because women aren’t baby factories in those countries. They have babies later (which leads to fertility problems) and they have fewer babies by choice.
Estrogen pollution is a potential problem. (Note: I am not vouching for everything in that article, since the site itself may not be a particularly objective one. However, the article does cite relevant research, and the problem is considered to be a potentially serious one by many researchers.)
Natural and artificial estrogen gets in the water supply through sewage, and also many natural pollutants chemically mimic the effects of hormones. These pollutants as of yet have not reallly received much attention, but could have some serious effects on fertility.
This said, this is not an intrinsic problem of human biology. Once identified, actions can be taken to keep these compounds out of the environment.
Regarding the OP, as has been said there is no real parallel between the situation in bulldogs and that in humans. The great drop in birth rates in industrialized countries is quite clearly linked to economic changes, rather than physiological ones in the population.
There is also a much higher infant mortality rate in less devloped countries and many of those countries have little access to or understanding of contraceptives.
I’m pretty sure that if there’s one thing this planet doesn’t need is MORE people. Other than maybe a nuclear war irradiating the population, I can’t imagine would would make the entire human race infertile.
Developed countries also have things like child labor laws and laws saying that children have to attend school. If a couple wanted to have lots of kids and send some of them to work to support the others, as is done in some less-developed countries and was done in the past in industrialized countries, they wouldn’t be able to do it (or at least wouldn’t be able to do it as easily).
And most IVF and other infertility treatments are performed on women who are past the “natural” age for childbearing. From an evolutionary standpoint, women should start having children at sexual maturity and continue through their twenties. Instead, women in industrialized nations frequently have a first child in their late twenties through thirties, and the age keeps skewing upward with the impetus to first undergo extensive post-secondary eduation and establish a career.
In any case, bulldogs are an example of extreme artificial selection, i.e. selecting for characteristics (via breeding) that are in no way reproductively or adaptively advantageous, except insofar as they please the (highly questionable) esthetic sensibilities of dog breeders.