Evolution of people within a generation?

[LightningInAJar]

TL;DR Summary

How does and doesn't evolution work in people?

Are there certain things that threaten human evolution or at least threaten to make us less functional as a species?

If for example we started living twice as long due to medical intervention with better health and started having children at twice the average age? Would it hurt much to have children less frequently, or can we evolve within generations to a good enough degree that we don't need to depend on procreation as much?

 

[Drakkith]

Are there certain things that threaten human evolution or at least threaten to make us less functional as a species?

What do you mean by 'threaten'? To quote wikipedia, "Evolution is change in the heritable characteristics of biological populations over successive generations." There's nothing to threaten here, as it's just a process that occurs over time without any kind of end goal in mind. We're not necessarily evolving into something intrinsically 'better' or more advanced.

Would it hurt much to have children less frequently, or can we evolve within generations to a good enough degree that we don't need to depend on procreation as much?

Having fewer children over a longer time would slow down evolution, since the time between generations is longer, but that's about it.

However, one consequence of modern medicine and technology is that deleterious genes are not being removed (by the death of their carriers prior to procreation) as often as before, but the enormous increase in our population from perhaps a few tens of thousands to over 7 billion has given us a vast reservoir of different genetic combinations. There are probably 100 times more people with 'good' genes now than there were total people back in the stone age.

 

[jedishrfu]

@Drakkith brings up an interesting point in that artificial longevity means bad genes stay around longer. Longevity with procreation evolution is slowed down a bit.

Biologically I’m not sure whether longevity would lead to the procreation time range being extended or not by that I mean what’s the latest age a woman could give birth If she could live much longer than before.

 

[Ygggdrasil]

@Drakkith brings up an interesting point in that artificial longevity means bad genes stay around longer. Longevity with procreation evolution is slowed down a bit.

Whether a certain variant of a gene is a "bad gene" (i.e. deleterious to fitness) depends a lot on the environment. The mutation that causes sickle cell anemia helps protect against malaria. Genes that make humans crave calorie rich foods that helped our hunter-gatherer ancestors are likely maladaptive in the developed world where obesity is a bigger problem than malnutrition.

Modern medicine has increased the genetic diversity of the human race by allowing the existence of traits that might otherwise have disappeared through natural selection. While this may seem bad from an evolutionary standpoint, this view misunderstands evolution as genetic diversity is a species' greatest asset in evolution. A population containing a diverse set of mutations provides the basis for a population to adapt to changes to the environment. What if some deleterious mutation that seems to impair some individuals' ability to function in some context provides immunity against the next worldwide pandemic? (Of course, modern medicine, not genetic diversity, is likely what will protect humanity against extinction in the face of a pandemic disease). Genetic diversity is an evolutionary strength not a weakness.

Finally, if one is worried about the future of the human race, there are much greater problems to worry about (climate change, nuclear weapons, etc.) than human genetics. (I'll also note that groups of people worried about the purity of human genetics have also posed major threats in the past as well!)

Biologically I’m not sure whether longevity would lead to the procreation time range being extended or not by that I mean what’s the latest age a woman could give birth If she could live much longer than before.

There could be technological solutions to extend the biological clock (e.g. see my answer here or this article from MIT Technology Review).

 

[LightningInAJar]

I am very interested in the latest aging research into NAD+, senescence, yamanaka factors being used to reverse epigenetics to early phases in life, etc. But I worry we don't know enough about DNA and what is a bad arrangement. I think only recently did we finish the human genome project minus a few parts of the Y chromosome. And I don't think we have the technology to computer record a person's whole genetic code beyond maybe 99.9% which seems like a significant inaccuracy. I worry that since we can't have a copy we had of our DNA from youth, that damage can never be "fixed" as what changed can't be known afterwards. This is why I ask if a person can become more adaptive over time without becoming worse off even with reverse aging techniques when they apply more to humans. Would we become a giant tumor eventually if our lifespan were indefinite? Is living briefly and having children young the only sure way to keep our species from turning to dang? Lol.

 

[Fervent Freyja]

Concerning epigenetics and methylation, methylated areas of DNA can be worked out through with analysis. Demethylation occurs naturally with age and especially with lifestyle/environmental changes. A person can improve demethylation through proper nutrition and better health decisions. I know a few therapies are being explored and this whole area of epigenetics is under heavy study. There's hope, we just don't know enough yet about methylation or histone modification and other mechanisms. It's all in the works.

It isn't that we don't have the technology. There are groups that can sequence an entire genome in around a month, even less. At the place I work there are people working hard at making it available within weeks and for a little over $1000, the same people that were a part of the human genome project to begin with. The Y chromosome has been entirely sequenced many times, I don't know why you think that it hasn't been. It isn't far-fetched to suppose that children of the future, hundreds of years from now, will be involved in projects at school where they sequence their own DNA. If we can reduce the cost to just a couple hundred dollars then I can see us being able to sequence the genomes of our newborns immediately after birth, as part of their health record. We currently have enough information to be able to predict problem areas with software and that ability will continue to increase over time. I imagine we would be able to understand evolutionary changes better when we can sequence the genomes of at least three generations and at numerous milestones for each generation.

Aging is complex and reverse epigenetics isn't going to solve the problem of aging, more so the quality of life for a single person. Humans need to improve their lifestyles and environmental changes need to be made because any therapy is only going to be temporary if a person does not correct that. For example, a person that was malnourished, abused, and endured prolonged suffering throughout childhood can amend some of the methylations naturally through time with better health and lifestyle decisions. Even then, parts of their DNA are still vulnerable to methylation reoccurring. I wouldn't consider those areas bad arrangements. The bad arrangement is usually more concerned with the external factors of a person. That's why nutrition, fitness, lifestyle choices, pollution/environmental problems, stress factors, mental health, sleep hygiene, etc. are so important and stressed by the health community.

Our species is going to blip out one way or another. Having children can be a joy and most people do it without the intention of continuing the species. Prolonging our lifespan without improving our quality of life is disastrous. Many people don't want to live past 80 or so.

 

[LightningInAJar]

Concerning epigenetics and methylation, methylated areas of DNA can be worked out through with analysis. Demethylation occurs naturally with age and especially with lifestyle/environmental changes. A person can improve demethylation through proper nutrition and better health decisions. I know a few therapies are being explored and this whole area of epigenetics is under heavy study. There's hope, we just don't know enough yet about methylation or histone modification and other mechanisms. It's all in the works.

It isn't that we don't have the technology. There are groups that can sequence an entire genome in around a month, even less. At the place I work there are people working hard at making it available within weeks and for a little over $1000, the same people that were a part of the human genome project to begin with. The Y chromosome has been entirely sequenced many times, I don't know why you think that it hasn't been. It isn't far-fetched to suppose that children of the future, hundreds of years from now, will be involved in projects at school where they sequence their own DNA. If we can reduce the cost to just a couple hundred dollars then I can see us being able to sequence the genomes of our newborns immediately after birth, as part of their health record. We currently have enough information to be able to predict problem areas with software and that ability will continue to increase over time. I imagine we would be able to understand evolutionary changes better when we can sequence the genomes of at least three generations and at numerous milestones for each generation.

Aging is complex and reverse epigenetics isn't going to solve the problem of aging, more so the quality of life for a single person. Humans need to improve their lifestyles and environmental changes need to be made because any therapy is only going to be temporary if a person does not correct that. For example, a person that was malnourished, abused, and endured prolonged suffering throughout childhood can amend some of the methylations naturally through time with better health and lifestyle decisions. Even then, parts of their DNA are still vulnerable to methylation reoccurring. I wouldn't consider those areas bad arrangements. The bad arrangement is usually more concerned with the external factors of a person. That's why nutrition, fitness, lifestyle choices, pollution/environmental problems, stress factors, mental health, sleep hygiene, etc. are so important and stressed by the health community.

Our species is going to blip out one way or another. Having children can be a joy and most people do it without the intention of continuing the species. Prolonging our lifespan without improving our quality of life is disastrous. Many people don't want to live past 80 or so.

Personally I wouldn't want to live past 80. If I could have my 20 year old health for life I'd gladly check out at 60. Odds are good I'd get done more in that state with twenty years fewer. If one wanted to know their original DNA sequence could they take many tissue samples and compare them to find changes and commonalities? Maybe in the worst case scenario "photo stack" them to average out errors?