How could we have stopped evolving?

[Boerseun]

The original post says something to the tune of "We haven't evolved since we became a species".

That's just ridiculous.

It's like saying "I haven't had a cup of coffee since my last cup of coffee".

Look around you. Everyone looks slightly different. That's evolution. Because not only are your ears slightly longer than mine, but your internal organs look slightly different (and might be slightly better or slightly worse in operation) than mine.

But because of the size of the human population and the good genetic communication existing between far-flung pockets of humanity (making the human race virtually one single gene pool), any evolutionary changes for the better or worse will simply be diluted to non-expression. Big populations well-suited to their environment rarely undergo evolutionary change. And we've got the knack of making the environment suit us. So, pressure for evolving into a certain niche is basically removed from the equation - we just panelbeat the niche to suit us. We've walked on the moon without having to evolve the ability to survive in space.

[Michaelangelica]

Originally Posted by Kayra

Personally, I have a few issues with the concept that humans are considered to be still evolving.

As I understand it, in order to evolve an environmental stressor must be present. If you are perfectly (or nearly so) suited to your environment then evolution is drastically slowed, with only minor improvements over long periods of time, just as was pointed out with the crocodiles and sharks.

I mentioned a few changes from the last 10,000 years in my last post.
All meet your requirement that an 'an environmental stressor must be present'
and, as Boreseun seems to be saying,among smallish gene pools (Andes Indians, Northern Europeans, etc). One I forgot was Sickle Cell Anaemia in Africa not killing but giving malaeria resistance . There are no doubt others too but this is not my field.

Changes due to epigenetics are not (as far as I can see) evolution. We are simply leveraging traits that we already possessed, not evolving new ones.

Yes we also have the genes for wings too. So how many have to jump of tall buildings before that becomes expressed?

Epigenetics itself however, was something that we evolved.

Bit of a circular argument?

We have, as a race, removed most environmental stressors in our lives

.
I don't think so.
Have you

• worked for a major corporation,
• been involved in a modern war?
• breathed the air in downtown LA, Bejing, or Mexico city?
• eaten food or drunk water contaminated with chemicals or pesticide in the food chain?

I think as the environment changes the stress changes too. The pace of change in the last 1-200 years has probably been too quick for us to develop adaptive genetic changes.

As a result, I would expect over the next 10-50 generations to see in increase in non-functional mutations creeping into our gene pool as we can medically deal with a considerably larger number of debilitating or crippling issues and still procreate, passing on these bad mutations.

Perhaps, but there are other factors at work too

• amniocentesis and medical abortion,
• the desire of the Chinese to have one BOY child,
• Aids epidemic esp in Africa
• increasing tolerance of single sex unions
• medical treatment of fertility problems
• possible medical discovery that Autusim and Down's syndrome may be wheat intolerance related. Perhaps there will be other medical advances in what we see as Genetic mutations.

The only place I expect to see evolution still in action is in third world countries, where those that are unfit for the harsh conditions do not live long enough to pass on those unfit traits.

Evolution or epigenetics?

What other stressors are out there?

see above

Here is an interesting article on agricultural development and genetic change
Evolutionary Discordance of Grains/Legumes in the Human Diet
It is interesting to reflect that

Anatomically modern Homo sapiens appear in the fossil record in Africa and the Mideast by about 90,000-110,000 years ago and behaviorally modern H. sapiens are known in the fossil record by ~50,000 years ago in Australia and by about ~40,000 yrs ago in Europe.

Not along time, genetically speaking.
some other specific changes I did not know about

— Carbohydrate metabolism: positive selection was observed for genes involved in breaking down mannose in Yorubans, sucrose in East Asians and lactose for Europeans. Mannose is a sweet secretion found in some trees and shrubs, sucrose is common table sugar, and lactose is a sugar found in milk, which most Africans and East Asians cannot digest as adults.

FOXNews.com - Study: Humans Still Rapidly Evolving - Science News | Science & Technology | Technology News

In East Asians, they found strong evidence of positive selection in genes involved in the production of alcohol dehydrogenase (ADH), a protein necessary for breaking down alcohol.
Many East Asians can't metabolize alcohol because they carry a mutation that prevents them from making ADH. The new finding suggests that the mutation may confer some currently unknown additional benefit.

Another Anti-malerial

Favism is an acute hemolytic anemia triggered by ingestion of fava beans in genetically susceptible subjects with severe deficiency of glucose-6-phosphate dehydrogenase (G6PD). G6PD deficiency is thought to confer protection against malaria only in those geographic areas where favism exists [Golenser 1983].
A substance in fava beans called isouramil (IU) triggers the hemolytic anemia in G6PD-deficient individuals, and it is this interaction of IU with G6PD erythrocytes which renders these red blood cells incapable of supporting the growth of the malarial pathogen (Plasmodium falciparum).
Thus, the spread of agriculture (fava beans in this case) to geographic locations surrounding the Mediterranean was responsible for the selection of G6PD in early farmers.

Males are supposed to Evolve faster than Females
(It's alright girls, it's because the male genetic make-up is 'simpler' )

This is fascinating too
If I had a spare $200 bucks I would do it.
Anyone know anyone who has?
DNA Tribes Personal Genetic Analysis

[charles brough]

As Kay indicates, there is not the stress that can and does cause evolution. World population has skyrocketed in a matter of 70,000 years. That is not the result of more biological evolution.

As Mike says, birds have evolved that fast, to exploit a vast new area of diverse food sources. So, they evolved enough to exploit them and in a short time. But we did not have to do that. We exploited the world's resources in a new and different way. This, I think, is what happened:

We could exploit the vast world's resources by adapting tools and building our tool culture into our ideological systems. We are unique in having speech so we could carry forward and improve this tool cultural heritage. Tool culture and the ideological system are related in this way: the more advanced the religion, the more people can explain things via natural cause and effect so that better (tool) technology can result.

This is, I believe, how we did it: Once we learned to speak we adopted common ideological systems so our hunting/gathering groups could grow into large societies. The common ideology could bind people into the larger groups even though we are "hard-wired" only for hunting-gathering-group-size.

This is, to me, the way social evolution works and logically explains what happened and is continuing to play out to this day.

[Michaelangelica]

I agree with what you say Charles except I do believe we have a number of environmental stressors. Over 40,000 man-made chemicals in our environment. Our seafood is contaminated, our offices full of toxins. Also food preservatives, dyes, flavor enhancers, synthetic and 'nature identical" flavours. Some may survive these stressors better than others. But certainly the number of kids with food related complaints like allergies, asthma, ADD and perhaps, even autism is soaring.

We also have the bodily stresor of sitting on our buts all day instead of ploughing fields ourselves or with oxen or chasing a four-legged dinner!

It may be that when we discovered cooking in fires this produced some mutations as it does now with burnt/charcoal food and promotion of cancerous mutations.

I found this little bit of information hard to explain.
You wonder how having cancer can be adaptive to the organism?

"Celtic Mutation" - A human cell defect leading to strands of breast
and ovarian cancer has been traced to Scotland, with claims that it
originated from an unknown person living in the southwest of Scotland
about 300 years ago and was passed on to hundreds of descendants
(published in The Guardian, 3/27/00; Brian Cohen, a researcher at St.
Andrews University)

Unhealthy Living

[Kayra]

Originally Posted by Michaelangelica

I mentioned a few changes from the last 10,000 years in my last post.
All meet your requirement that an 'an environmental stressor must be present'
and, as Boreseun seems to be saying,among smallish gene pools (Andes Indians, Northern Europeans, etc). One I forgot was Sickle Cell Anaemia in Africa not killing but giving malaeria resistance . There are no doubt others too but this is not my field.

Your last post contained only a vague reference to Galapagos birds, with no specifics. It is true that they did meet the requirements of an environmental stressor, and so evolved to fit their new niches.

Sickle Cell/malaria is a wonderful example of a stressor as well. Exactly what I was looking for.

Originally Posted by Michaelangelica

Yes we also have the genes for wings too. So how many have to jump of tall buildings before that becomes expressed?

Can I assume this was a tongue in cheek statement and not a serious question?


Epigenetics itself however, was something that we evolved.

Originally Posted by Michaelangelica

Bit of a circular argument?

Nope. At least I do not think so.
Epigenetics is the ability for a cell (or multi cellular creature) to pass on characteristics to daughter cells without a change in genetic makeup. This is critical for stem cells to be able to become any other type of cell in our body. Once it commits to being a cell of a particular type, all of it's daughter cells assume the same identity, with no change in genetic makeup.

Life here evolved this ability (as did all multicellular life we know of), and leverage it to allow for the vast array of creatures that now exist.

Epigenetics has evolved into a system that allows life to adapt to a sudden change in environment without the need to evolve these changes. The adaptations this allows are a basic part of us, each exist and has already evolved. They only await the right conditions to express themselves.

When you lift weights, your body adapts to the changing physical requirements and grows more muscles. This is not an evolutionary change, but expression of an adaptation we already possessed.

Not really a circular argument I think (although I have been known ot miss these sneaky things before )

We have, as a race, removed most environmental stressors in our lives

Originally Posted by Michaelangelica

I don't think so.
Have you

• worked for a major corporation,
• been involved in a modern war?
• breathed the air in downtown LA, Bejing, or Mexico city?
• eaten food or drunk water contaminated with chemicals or pesticide in the food chain?

I think as the environment changes the stress changes too. The pace of change in the last 1-200 years has probably been too quick for us to develop adaptive genetic changes.

Environmentally stressing small (compared to the total world population), non-isolated groups of people is unlikely to create a true, persistent evolutionary change in mankind.

Remember that for an evolutionary change to persist it MUST have a net positive chance for those genes to be passed on more then someone without those genes. Your sickle cell example fits this perfectly

Unfortunately, none of the examples in your list do.


I am still unconvinced that we are still in a state of positive evolution. We are very well suited to our current environment, and those we are not suited to we change until they suit us.

With the limits of our environment being relaxed, our genome has a chance to try a wider range of genetic mutations (as they have evolved to do), so long as these changes do not limit reproduction.

Historically speaking, this is a VERY recent change and has likely had only minimal impact on the human genetic makeup. Only first world countries will likely see any changes, and they are not likely to be specific adaptations that you can point at as say "Look, this trait is evolving in us". More likely, we will see a general increase in genetic disorders, cancers, bad eyesight, more premature births, unfitness, and poor ability to adapt to changing environments.

The only upside to this is that the human race will be gaining in genetic diversity faster then anything on the planet today. I think it would be highly unlikely that any natural pandemic could seriously impact the fate of mankind at this point.

If we want to further evolve, I would have to say the onus is on us to make it happen, and we are.


OK, yet another long winded post from me. Sorry about that

[Michaelangelica]

Originally Posted by Kayra

Your last post contained only a vague reference to Galapagos birds, with no specifics.

Sorry, last but one

There have been a number of genetic changes in the last 10,000 years.
EG:-
1. Ability to digest lactose
2 Loss of ability to manufacture Vitamin C
3. Among those who live in high altitudes, the ability to access oxygen more efficiently.
5. The ability to digest gluten.
6. Resistance to many diseases such eg AIDs, due to exposure to c 10-15C plague virus. Also small pox and measles resistance among Europeans.

Can I assume this was a tongue in cheek statement and not a serious question?

Yes and no, there is a lot of "junk" DNA there waiting for somebody/thing to turn it on.

Epigenetics itself however, was something that we evolved.

Nope. At least I do not think so.
Not really a circular argument I think (although I have been known ot miss these sneaky things before )

Thanks for the further explanation. I see your point. I am still not sure that I really understand this. Genetic material that is just close to other genetic material can turn it on. As in the experiment producing chickens with teeth.( see Darwin re-visited thread) Is this epigenetics?
Epigenetics to me is like a ball (development/growth) rolling down a valley, it has a lot of possible routes (epigenetics) while the DNA just proscribes the walls of the valley which the ball must follow.
Did we evolve this system or has it always been like this?
Sorry if this sounds confusing (but I am a little.)

We have, as a race, removed most environmental stressors in our lives

We will have to agree to disagree on this.
I feel we have just changed our stressors. Those with super liver and kidneys will be the ones surviving plastics and other chemicals in the food chain.
(Unless of course the phyto-plankton collapse first-then we don't need to worry we will all be dead.)

Many Corporations seem to operate with a consistent "background noise" of psychological, performance and time stressors unlike any we have seen before.
We no longer respond to the seasonal and diurnal rhythms of nature. We don't have Winter 'off' work. We don't go to bed when it gets dark. We don't eat seasonal, fresh foods.

Unfortunately, none of the examples in your list do.

Please re-check list; there may be others in the 'Darwin Re-visited' thread.

I am still unconvinced that we are still in a state of positive evolution. We are very well suited to our current environment, and those we are not suited to we change until they suit us.

A retro-virus could decide to change us tomorrow. perhaps unlikely, but it has happened before (see parasites thread)

With the limits of our environment being relaxed,

an assumption I don't have evidence for.

our genome has a chance to try a wider range of genetic mutations (as they have evolved to do), so long as these changes do not limit reproduction.

How come they would decide to do this; if, as you propose, they are not stressed?

Historically speaking, this is a VERY recent change and has likely had only minimal impact on the human genetic makeup. Only first world countries will likely see any changes, and they are not likely to be specific adaptations that you can point at as say "Look, this trait is evolving in us". More likely, we will see a general increase in genetic disorders, cancers, bad eyesight, more premature births, unfitness, and poor ability to adapt to changing environments.

I am not sure i follow your logic here
Therapeutic abortion /amniocentesis is cutting down the number of births with genetic disorders.
We may soon have in-utero genetic surgery for some genetic disorders.
Also we are more aware of environmental stressors that turn on disease EG MS occuring more as you move away from the equator. Down's syndrome and gluten sensitivity.
A lot of the health problems you list can be accounted for by the fact we are living a lot longer than we ever used to. Eyesight, cancer, unfitness, adaptability are age related, if not always necessaryly down to age. In the west we ale living twice as long as we did 100 years ago.

Premature births may be too, age related as women decide to have babies at 35 instead of 15-18YO. Certainly your chances of having a Down's Syndrome (Trisomony 22/3?) baby increases with mother's age.

The only upside to this is that the human race will be gaining in genetic diversity faster then anything on the planet today.

Yes I agree. But mainly bought about by cheap travel and intermixing of once isolated human societies. Will that be all positive? What will we loose?

I think it would be highly unlikely that any natural pandemic could seriously impact the fate of mankind at this point.

I disagree a bird flu pandemic has the potential to wipe out the prime breeding ages of mankind, as it did in 1918. We have not beaten viruses yet.
The anti-virals we are stockpiling, for such an event, are a joke.
A psychological/political palliative at best.

If we want to further evolve, I would have to say the onus is on us to make it happen, and we are.

Yes I agree, seems we will be doing this soon. "Lets just shuffle a few genes and see what happens. . ." I can't see that it is wise; but I don't see anything that will stop it.

OK, yet another long winded post from me. Sorry about that

Don't be sorry. If you can't be long-winded at hypography where can you be? There are many others, including me, vying for the "Hypography Chief-Longwindedness Trophy"

[Kayra]

Originally Posted by Michaelangelica

Yes and no, there is a lot of "junk" DNA there waiting for somebody/thing to turn it on.

I would hazard a guess that the entire population of the earth could jump off that tall building and not a single one would spontaneously sprout wings.

Originally Posted by Michaelangelica

Thanks for the further explanation. I see your point. I am still not sure that I really understand this. Genetic material that is just close to other genetic material can turn it on. As in the experiment producing chickens with teeth.( see Darwin re-visited thread) Is this epigenetics?
Epigenetics to me is like a ball (development/growth) rolling down a valley, it has a lot of possible routes (epigenetics) while the DNA just proscribes the walls of the valley which the ball must follow.
Did we evolve this system or has it always been like this?
Sorry if this sounds confusing (but I am a little.)

Nice analogy
Our DNA contains within it the ability to bootstrap an Epigenetic system that controls the DNA as we grow from Egg/Sperm to complete life form. If it is not in our DNA, Epigenetics can not create it. We needed to evolve a trait at the DNA level before any aspect of it can be used by Epigenetics. Epigenetics though can make surprising use genetic traits to create unexpected results.

We have, as a race, removed most environmental stressors in our lives

Originally Posted by Michaelangelica

We will have to agree to disagree on this.
I feel we have just changed our stressors. Those with super liver and kidneys will be the ones surviving plastics and other chemicals in the food chain.
(Unless of course the phyto-plankton collapse first-then we don't need to worry we will all be dead.)

Many Corporations seem to operate with a consistent "background noise" of psychological, performance and time stressors unlike any we have seen before.
We no longer respond to the seasonal and diurnal rhythms of nature. We don't have Winter 'off' work. We don't go to bed when it gets dark. We don't eat seasonal, fresh foods.

When I was speaking of environmental stressors, I meant those that affect natural selection. These are the only stressors that will affect DNA or the evolutionary process. Without them the only evolutionary process left is Genetic Drift, and that does not work in large populations.

With that in mind, we have removed environmental stressors that affect natural selection. Being stressed at work is unlikely to have a significant effect on a large populations ability or chance to reproduce and pass on genes.

Originally Posted by Michaelangelica

A retro-virus could decide to change us tomorrow. perhaps unlikely, but it has happened before (see parasites thread)

Yes, it is possible.

With the limits of our environment being relaxed,

Originally Posted by Michaelangelica

an assumption I don't have evidence for.

Lets see.
We can make it warm when it is cold and cold when it is warm
Move water over great distances to water crops.
Move food to any place in the country to alleviate starvation.
Most diseases can be cured or the symptoms reduced sufficiently that survival rates past procreation age are astronomically high.

Food, shelter, and basic medical services are available to the majority of the population. Even the weak, dull witted, and unmotivated can get a job stuffing bags at the local grocery and make sufficient income to support a family and procreate.

The evidence is pretty overwhelming I am afraid.

our genome has a chance to try a wider range of genetic mutations (as they have evolved to do), so long as these changes do not limit reproduction.

Originally Posted by Michaelangelica

How come they would decide to do this; if, as you propose, they are not stressed?

The more severe the stressors in an environment, the more critical it is to be perfectly suited to that environment as those are the life forms most likely to survive. Reduce the severity of the stressors, and a wider range of general unfitness can survive and reproduce. With that comes wider genetic diversity.
It is not a decision, simply cause and effect.

More likely, we will see a general increase in genetic disorders, cancers, bad eyesight, more premature births, unfitness, and poor ability to adapt to changing environments.

Originally Posted by Michaelangelica

I am not sure i follow your logic here
Therapeutic abortion /amniocentesis is cutting down the number of births with genetic disorders.
We may soon have in-utero genetic surgery for some genetic disorders.
Also we are more aware of environmental stressors that turn on disease EG MS occuring more as you move away from the equator. Down's syndrome and gluten sensitivity.

Wonderful technology based solutions to biology based problems.

Originally Posted by Michaelangelica

A lot of the health problems you list can be accounted for by the fact we are living a lot longer than we ever used to. Eyesight, cancer, unfitness, adaptability are age related, if not always necessaryly down to age. In the west we ale living twice as long as we did 100 years ago.

Remove all age related issues (as anyone over the age of reproduction to not drastically affect natural selection except in how they aid the family unit) and I believe you will still see an increase, and it will continue exponentially. The more technology alleviates genetic based issues without actually resolving them at a genetic level that can be passed on to our children (I forget the word) , the greater the compounding of the problem over time. Genetic manipulation is the only solution mankind now has at his disposal. We are victims of our own success at technology.

P.S. I never took much stock in the saying that we are living twice as long as before. They tend to average in child deaths and that brings the average lifespan WAY down. The fact is, the maximum lifespan has never really changed significantly, and if you lived past childhood 100 years ago you had about the same change at living to 100 as you do today.

Originally Posted by Michaelangelica

Premature births may be too, age related as women decide to have babies at 35 instead of 15-18YO. Certainly your chances of having a Down's Syndrome (Trisomony 22/3?) baby increases with mother's age.

A VERY valid point.

Originally Posted by Michaelangelica

Yes I agree. But mainly bought about by cheap travel and intermixing of once isolated human societies. Will that be all positive? What will we loose?

Wouldn't cheap travel perpetuate diversity and not create it?

I think it would be highly unlikely that any natural pandemic could seriously impact the fate of mankind at this point.

Originally Posted by Michaelangelica

I disagree a bird flu pandemic has the potential to wipe out the prime breeding ages of mankind, as it did in 1918. We have not beaten viruses yet.
The anti-virals we are stockpiling, for such an event, are a joke.
A psychological/political palliative at best.

In 1918 the worst pandemic in recorded human history struck the human population. It traveled to the most remote regions of our planet including the arctic and the Polynesian islands. It had a preference for killing people that were just before the age of reproduction. It had a DEVESTATING mortality rate and was a monster at infecting people (50%?). Over 100,000,000 dead by some estimates. It was a Pandemic of amazing proportions.

And yet...with all that going for it... we survived relatively unscathed as a race. We lost 5% of our population and we carried on.

Even a pandemic that wipes 99% of the population (and I have a hard time believing something of that nature could naturally evolve and not mutate immediately into something less severe) would still leave the planet with sufficient genetic stock to repopulate the earth. And we would, due to our social nature and technical knowledge.

I do not believe that we, as a race, are any longer subject to death by a natural biological factor.

Our evolution can still be shaped and affected by a pandemic, or any large scale persistent disease, but even those effects are coming to an end. As we start to truly understand the processes of life itself, inevitable means of dealing with diseases will be invented or discovered that life itself cannot easily circumvent. Technology WILL trump evolution, it is only a matter of time.

[Michaelangelica]

Originally Posted by Kayra

I would hazard a guess that the entire population of the earth could jump off that tall building and not a single one would spontaneously sprout wings.

Yes I must think of a better stressor than hard concrete
It is so unforgiving
Still it makes for good comics and Heros' will probably run on TV for years.

Our DNA contains within it the ability to bootstrap an Epigenetic system that controls the DNA as we grow from Egg/Sperm to complete life form.

That's interesting please tell me more

When I was speaking of environmental stressors, I meant those that affect natural selection.

So was I.
So we will have to agree to disagree. I think there are aspects of our 20C environment that could have the potential of impacting on evolution.
Plus
what will the survivors of Aids be left with? (We have only one documented so far) Plague survivors were given some immunity to aids 500 years after the main plague events.

the only evolutionary process left is Genetic Drift, and that does not work in large populations.

I have never been able to get my head around the statistical logic of this.
It seems to me that the planet is made up of a lot of small even tiny groups. Not just in the jungles of New Guinea but I have met people in UK, Europe and USA who have never in there lives moved more than 20-50 miles from their homes.
(In Germany I found a lady who spoke an Anglo-Saxon/latin dialict!)

Being stressed at work is unlikely to have a significant effect on a large populations ability or chance to reproduce and pass on genes.

Stress affects every organ in the body. I see it as a much more powerful thing than you do. This is probably the difference in our argument. Those that thrive in this stress get more power ,finances etc to reproduce and to protect their family, sometimes for generations.

With the limits of our environment being relaxed,

Lets see.
We can make it warm when it is cold and cold when it is warm

OK I didn't understand what you meant. You meant we have more control over our environment? Will Global warming change this? It certainly seems to have the potential to

Food, shelter, and basic medical services are available to the majority of the population.

The majority on Earth? i hope you are right. Have you seen typical Chinese family living. Two families in a shead too small for my lawnmower.

Even the weak, dull witted, and unmotivated can get a job stuffing bags at the local grocery and make sufficient income to support a family and procreate.

On USA wages?
Also in "Sheltered Workshops". If someone dosn't try to sterilise them First

our genome has a chance to try a wider range of genetic mutations (as they have evolved to do), so long as these changes do not limit reproduction.

The more severe the stressors in an environment, the more critical it is to be perfectly suited to that environment as those are the life forms most likely to survive. Reduce the severity of the stressors, and a wider range of general unfitness can survive and reproduce. With that comes wider genetic diversity.
It is not a decision, simply cause and effect.

We both start with different assumptions here; so I can't really agree with your conclusion.
Are you saying because we (or at least some of us) protect the weak, and do not leave them to die on hillsides, the level of genetic mutations will rise?

More likely, we will see a general increase in genetic disorders, cancers, bad eyesight, more premature births, unfitness, and poor ability to adapt to changing environments.

Where do you draw the line between the two?
Someone recently argued to me on hypography that man's genetic manipulations (eg weedicide resistant Canola) was Natural Selection in action.

Remove all age related issues (as anyone over the age of reproduction to not drastically affect natural selection except in how they aid the family unit) and I believe you will still see an increase, and it will continue exponentially. The more technology alleviates genetic based issues without actually resolving them at a genetic level that can be passed on to our children (I forget the word) , the greater the compounding of the problem over time. Genetic manipulation is the only solution mankind now has at his disposal. We are victims of our own success at technology.

No, I don't "get" this
I have mentioned amniocentesis and mediacal aborts a couple of times. These are routinely performed on pregnant women over 30-35 and also those with a family history of genetic disorders.
This probably only happens in industrialised countries but it is certainly widespread here.
Humans have been culling the week, infirm, insane from their ranks for 10,000-100,000 years. Have we seen any lessening of genetic abnormalities?
It seems ever now and again anew genetic problem turns up (See the Scottish Cancer example previous post)
I worked in award of severely genetically abnormal young children & babies. Some looked like monkeys. They needed 24 hour care. The ward still haunts me. These kids will never reproduce. Perhaps one of them might be the progenitor of human ability to sprout wings and fly?

P.S. I never took much stock in the saying that we are living twice as long as before. They tend to average in child deaths and that brings the average lifespan WAY down. The fact is, the maximum lifespan has never really changed significantly, and if you lived past childhood 100 years ago you had about the same change at living to 100 as you do today.

I meant longevity rather than lifespan. Homo sapien's Lifespan has not seemed to change for a very long time and even new longevity methods (calorie restricted diet etc) don't seem to have much effect on this. Technology could change this (recent research with long living mouse skin)
PS.
Do I hear a slight note of pedantry creeping in here?

Wouldn't cheap travel perpetuate diversity and not create it?

That is what I was proposing

It will also help a pandemic move across the world with a speed that will make the 1918 bird flue look like model T Ford.

I do not believe that we, as a race, are any longer subject to death by a natural biological factor.

Well at the moment is is a bit of an academic argument.
I would feel a little safer if Russia and the USA destroyed their biological weapons. I would also like to see some serious wins on the AIDS, drug resistant tuberculosis, and malaria front. Especially in Africa.
I hope your faith in technology is correct. (Do we spend more on wars and armaments or medical research I wonder?)

Technology WILL trump evolution, it is only a matter of time.

It seems to me amazing. that the might & Titan of Technology that is the USA, can't eradicate plague from its borders.
I think it would be highly unlikely that any natural pandemic could seriously impact the fate of mankind at this point.

I do not believe that we, as a race, are any longer subject to death by a natural biological factor.

Our evolution can still be shaped and affected by a pandemic

,
yes

[charles brough]

Really, you guys! Can't we have shorter and more concise posts? I would love to know what you are thinking but is it worth all that reading? I am partial to just two or three paragraphs. I guess I'm an "outsider" there and will have to pick up on a different thread . . .

[Kayra]

Originally Posted by charles brough

Really, you guys! Can't we have shorter and more concise posts? I would love to know what you are thinking but is it worth all that reading? I am partial to just two or three paragraphs. I guess I'm an "outsider" there and will have to pick up on a different thread . . .

Heh, I really must appologize for that friend. I have never been known for my consise posts

I stopped discussing this as there are to many points that I do not seem to be able to get across, and I place the blame entirely on my inability distill what I have to say.