How could we have stopped evolving?

[CraigD]

I don't think Cochran/Hawks in World Science report is correct about our evolution stopping.

Though I can see how one would get the impression from posts such as the first in this thread:

In March 2007, Cochran/Hawks in World Science reported that the main genetic changes that have taken place in us in the last almost 200,000 years have merely been a slight shrinking of body and brain size and changes in metabolism!

An actual read of the World Science article “Human evolution, radically reappraised” reveals that it reports a claim almost exactly the opposite of the claim that human evolution has stopped. The first sentence of the article reads

Human evolution has been speeding up tremendously, a new study contends—so much, that the latest evolutionary changes seem to largely eclipse earlier ones that accompanied modern man’s “origin.”

I’m puzzled how charles brough interpreted the article as a claim that humans have stopped evolving, though I believe his reasoning has something to do with the difficult-to-precisely-define biological term “species”, and the not unreasonable belief that biological evolution in humans has become less significant in many ways than changes in human society.

 

:) It’s wise, I think, to reread a source before repeating conclusions made about it. In this case, we appear to have twisted our impression of the article in question to almost the exact opposite of its actual message! :D

[nutronjon]

Well good.

 

Last night's show about starvation around the world, is so pressing on me at the moment, it seems silly to argue the evolution issue, so I am glad there is no serious arguement going on here. The only reason I get involved in such arguments, is to oppose superstitious notions, so we can get down to the work that really needs to be done.

[PocketLint]

Having very, very poor eyesight and very very large glasses to correct the situation, I have often wondered how I would have survived during the era(s) where our species experienced vast changes in our biological features.

 

 

There would have been no Lens Crafters to help me see. I could not have hunted my own food. I would have been a burden on any 'clan' to feed. I would have passed on long before I could sire any children, who would most likely inherit my poor eyesight based on the fact that my 4 kids current wear glasses also.

 

 

So, bouncing around in the back of my head is the idea that mankind's ability to harness technology has played a very large role causing our evolutionary changes to plateau.

 

 

-Bob

[Michaelangelica]

 

So, bouncing around in the back of my head is the idea that mankind's ability to harness technology has played a very large role causing our evolutionary changes to plateau.

 

 

-Bob

There is a lot of archaeological evidence that injured humans (broken bones, arrow wounds (with the arrow head still in situ) ,trepanned skulls, arthritis) were cared for by early humans and I think Neanderthals too.

So the evolution of a caring society changed evolution?

 

You may have been the Monet of the tribe?

(The world looks like one of his paintings to me without my glasses)

[PocketLint]

There is a lot of archaeological evidence that injured humans (broken bones, arrow wounds (with the arrow head still in situ) ,trepanned skulls, arthritis) were cared for by early humans and I think Neanderthals too.

 

 

 

I was referring to genetic issues more than environmental. It's not inconceivable to me that someone with a broken arm might get cared for as they will eventually be able to function again in some capacity.

 

What about the person with diabetes or inherited heart valve issues they would surly die out long before their genes could be passed on to later generations with or without societal care.

 

I guess survival of the fittest kind of thing. For the most part, we no longer have that mechanism as one of the cogs of evolution in play.

 

Don't get me wrong. I'm in no way suggesting this is a bad thing. I would not want to exist in a society that did not care for it's infirm.

 

I was just trying to answer the original question. "How could we have stopped evolving?'

 

 

 

-Bob

[Moontanman]

I don't think this is true.

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.

 

While I am not sure about the other things you are proposing strike the vitamin C thing. All great apes share this trait with us and it almost certainly evolved several million years ago.

[DFINITLYDISTRUBD]

We ain't done evolving...

Humans will get smaller and dumber in a few thousand years or so...A direct result of having machines do all the thinking and remembering for us and our insatiable need and love of mechanised transport...size and smarts simply won't be needed so with lack of use for a few few generations:shrug:

[CraigD]

So, bouncing around in the back of my head is the idea that mankind's ability to harness technology has played a very large role causing our evolutionary changes to plateau.

Take care to read the actual March 2007, Cochran/Hawks in World Science from which the original post of this thread drew the conclusion that humans have stopped evolving. In particular, note that it begins:

Human evolution has been speeding up tremendously, a new study contends—so much, that the latest evolutionary changes seem to largely eclipse earlier ones that accompanied modern man’s “origin.”

Rather than supporting it, Cochran and Hawks’s research suggests almost exactly the opposite of a present-day plateau in human evolution.

Having very, very poor eyesight and very very large glasses to correct the situation, I have often wondered how I would have survived during the era(s) where our species experienced vast changes in our biological features.

 

There would have been no Lens Crafters to help me see. I could not have hunted my own food. I would have been a burden on any 'clan' to feed. I would have passed on long before I could sire any children, who would most likely inherit my poor eyesight based on the fact that my 4 kids current wear glasses also.

Rather surprisingly, there appears to have been little detailed research of the genetics of nearsightedness. As far as I can tell, this 2005 “gene scan” study is the first broad study of it, and is very preliminary. This is less surprising when one considers that, compared to other heritable disorders, such as diabetes, nearsightedness has very little lethality, and, as wearers of very thick glasses and recipients of radial keratomy surgery know, can be very effectively managed.

 

The preliminary research indicates that, as was expected from empirical observations, nearsightedness involves many genes, with complicated dominance-recessiveness characteristics, so it’s unclear how common it was among prehistoric, or even historic humans up prior to fairly recent times. It’s also unclear how important to survival and reproduction good eyesight was among prehistoric humans – unlike the literacy requirements of recent industrial and “information age” society, one can argue that ancient hunter-gatherer society required little more from many of its members than the ability to perceive large objects at close range, a good sense of smell, taste, and touch, and appropriate cognitive and memory skills. It’s even reasonably to speculate that poor vision might have resulted in early social specialization, as humans unable to see well enough to run and hunt assumed “high tech” roles of a more intellectual nature (ie: “cave geeks” :thumbs_up). If this was the case, bad-eyesight genes may actually have had an important positive effect on our species survival and growth, and been selected for, not against.

[DFINITLYDISTRUBD]

one can argue that ancient hunter-gatherer society required little more from many of its members than the ability to perceive large objects at close range, a good sense of smell, taste, and touch, and appropriate cognitive and memory skills.

So us farsighted folks must have been the lookouts..eh?:thumbs_up

(You'd think there'd be more of us than even normal sighted folk as we could see the various large carniverous critters comin to dinner alot sooner:hihi:)

[PocketLint]

It’s even reasonably to speculate that poor vision might have resulted in early social specialization, as humans unable to see well enough to run and hunt assumed “high tech” roles of a more intellectual nature (ie: “cave geeks” :thumbs_up).

 

CraigD, you gave me a new way to look at it (pun intended).

 

After all, If I was unable to join the hunt, then I'm the one left behind with all the women folk in the cave. maybe that explains why all the kids keep bumping into the walls and calling the nearest tree dada.

 

If what you propose has merit, then nearsightedness might be the first genetic defect that works opposite of natural selection.

 

You actually have caused me to do a 180 in my thought process on this one.

 

 

This is less surprising when one considers that, compared to other heritable disorders, such as diabetes, nearsightedness has very little lethality, and, as wearers of very thick glasses and recipients of radial keratomy surgery know, can be very effectively managed.

 

 

My point exactly, NOW we have effective ways of dealing with nearsightedness. Prehistoric times? Well I can not be sure but I doubt RK was an option.

 

 

-Bob

[Michaelangelica]

While I am not sure about the other things you are proposing strike the vitamin C thing. All great apes share this trait with us and it almost certainly evolved several million years ago.

Whatever you say

The other five traits have evolved in the last 10,000 years

 

One order as a whole (Chiroptera) seems to lack synthetic ability. All the families tested (5) from one suborder of Primates lack the ability, whereas those (2) from the other suborder make the vitamin in the liver.

McCluskey, E. S. --- Which Vertebrates Make Vitamin C?

Homo sapiens, guinea pigs, monkeys, bats, some fish and many birds, do not produce their own vitamin C. The rest of the animal kingdom synthesizes their own vitamin C. For them, ascorbic acid is a hormone, not a dietary-acquired vitamin. Animals employ different organs to produce vitamin C

. Can Humans Live Longer?: The Missing Anti-Aging Hormone

[CraigD]

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.

While I am not sure about the other things you are proposing strike the vitamin C thing. All great apes share this trait with us and it almost certainly evolved several million years ago.

Whatever you say

I think MTM’s claim that the lack of vitamin C synthesis in all great apes, including humans, and a origin of this shared trait far older than 10,000 years ago, is well supported.

 

McCluskey, E. S. --- Which Vertebrates Make Vitamin C? (which Michaelangelica cites) shows via direct biological measurement that the ability to synthesize vitamin C is present in the prosimian (eg: lemurs, lorises, and tarsiers), but not the anthropoid (eg: monkeys and apes, including humans) branch of the primate evolutionary tree. The prosimian-anthropoid split is believed to have occurred 37 to 55 million years ago (sources: http://www.hopkinsmedicine.org/geneticmedicine/plos.pdf, PLoS Genetics: Population Bottlenecks as a Potential Major Shaping Force of Human Genome Architecture), making it likely that this anthropoid primate trait is very old, nearly as old as the primate order itself, which is believed to be about 60 to 65 millions years old (source: Early Primate Evolution:* The First Primates).

 

Interestingly, the prosimian-anthropoid division is somewhat taxonomologicaly incorrect. A genetically more descriptive taxonomy replaces the prosimian and anthropoid suborders with Strepsirrhini (eg: lemurs) and Haplorrhini (eg: monkeys, apes, and tarsiers). So the seeming exception of tarsiers (which are classified under the older nomenclature as prosimian) inability to synthesize vitamin C is resolved, tarsiers having spit along haplorrhini-strepsirrhini lines with monkeys, apes, etc. from the other prosimians, lemurs, lorises, etc. The vitamin C synthesis trait is one of the key data that lead to this change in taxonomy.

The other five traits have evolved in the last 10,000 years

Though I’ve not checked them in detail, I believe Micheaelangelica is right about these, though I’m uncertain if all of these traits can be considered human species-wide or unique among primates.

 

For example, taking

3. Among those who live in high altitudes, the ability to access oxygen more efficiently.

This trait, to the best of my knowledge, is fairly well understood to be related to genetic variance in Myoglobin genes, most notable in comparisons of high-altitude-dwellers (eg: Tibetans), with low-altitude-dwellers (eg: most humans). Although there are distinct, recognized gene variants (alleles) among these different populations, (see, for example, Mary Ann Liebert, Inc. - High Altitude Medicine & Biology - 3(1):39) they’re readily cross-heritable – One or a few generations of interbreeding between, say, Tibetans and Texans, the genes would be present in both sub-populations, along with many other, more visible ones, such as height, complexion and hair color. Although I’ve seen no studies of it, I suspect that this genetic diversity is present in the wide human population, among other primates, and even among the whole mammal class and more widely in the animal kingdom. In short, I suspect that a population of gorillas, rats, or even birds or other animals dwelling at high altitude for several generations would show an increased frequency of myoglobin genes optimized for the thinner air, and that these genes were present with about the same frequency in our ancestors 10s of thousands and millions of years ago.

Can Humans Live Longer?: The Missing Anti-Aging Hormone

This and other writing on genetics and life-extension therapy by health journalist Bill Sardi, should IMHO be taken with great skepticism. Statements such as “humans have the capacity to live for hundreds of years” and “of course, mutations are destructive and regressive, not progressive advancements of the genome.” supported only by references such as “An examination of the historical records of the Holy Bible reveals that Adam was recorded to have lived for 930 years (Genesis 5:5), and Noah for 950 years (Genesis 9:29)” fail to meet the usual standard for biological or medical writing – although some of Sardi’s health care advice (in articles other than the linked one), such as the tharaputic use of dietary supplements containing resveratrol, is not unreasonable, and supported by preliminary scientific evidence. In this article, however, Sardi fails to even address the question of whether, as he suggests, “the enzyme to produce vitamin C be re-installed in humans” or other animals is in way more beneficial than receiving it in our usual diet. His unsupported claim that “Humans once made vitamin C in their liver by the production of four enzymes which convert circulating sugars into ascorbic acid (vitamin C).” entirely contradicts the conventional theory described early in this post. While intriguing, his claim that “mammals who make their own vitamin C can live 8-10 times beyond their age of physical maturity. Mammals without this ability have a difficult time reaching 3-4 times” is likewise unsupported and incredible.

[HydrogenBond]

The inability to make vitamin C does not seem evolutionary. It appears to be the opposite. This lost may have been an artifact of having a food source containing vitamin C, such that the body didn't need to produce it like it used to. The same thing could happen to solar based vitamin D. If we avoid the sun and use high level sunscreens we may de-evolve this ability. It would be de-evolutionary in the sense that it limits human options for survival. It is hard for me see how this brings humans selective advantage.

 

One area where evolution seems to be targeting is the brain. This is subtle but is easy to see with an analogy. If the liver suddenly was able to process a whole new range of chemicals, one would call that evolutionary. The brain has evolved in the sense it is able to process a wider range of neural interactions. Neural interactions are not specific chemicals that are easy to differentiate as x or y, but these increasingly complex interactions are the stuff the brain is designed to process.

 

It may our inability to see a specific memory or the how this memory is organized in the brain, that makes this harder to see. We tend to look for a new chemical instead of changes in dynamic structures.

[Kayra]

One area where evolution seems to be targeting is the brain. This is subtle but is easy to see with an analogy. If the liver suddenly was able to process a whole new range of chemicals, one would call that evolutionary. The brain has evolved in the sense it is able to process a wider range of neural interactions. Neural interactions are not specific chemicals that are easy to differentiate as x or y, but these increasingly complex interactions are the stuff the brain is designed to process.

 

What I do not understand (please, no jokes on this point :) ) is what is the selection pressures for modern evolution in man? (The last 100 years)

 

As I understand it, evolution's chief means of bringing about a change in our genetic structure is to weed out the chaff or encourage higher reproductive rates. Weeding is likely to be FAR more effective and would produce more drastic results in a shorter time scale while more successful reproduction would be more effective in long term fine tuning to an environment in which most individuals can survive in past reproductive age.

 

With the exception of social bias and 3rd world countries, I do not see any environmental pressures that would bring about an evolutionary change in man anymore. Even those people that are more successful in our society are not more likely to reproduce then those that are not. As a clan we provide for our less successful members and assure their survival, to our ultimate genetic deficit.

 

With such a large population base and no means of long term isolation, advantageous genetic changes would likely have near 0 statistic impact as well.

 

So my question is, What is driving modern evolution in our day and age?

[HydrogenBond]

Maybe the confusion is because the brain produces a different type of output than purely biochemical, i.e., thought or action. These can lead to biochemical changes, in an indirect way. For example, learning to cook meat with fire was a brain output product. The affect of the output activity changed the way we digest meat. This change was not the big buck getting the females to make babies. It could be an old buck (man) with an activity that helps all the babies.

 

Have you ever heard of the saying brain children. This sort of hints upon the evolutionary parallel for the brain. The brain does not make biological children, but it can make brain children, which are ideas, art, etc. It is sort of analogous to asexual reproduction, where the mental womb is formed through education and experience. One of the brain children of Thomas Edison was the light bulb. He was a very prolific procreator of brain children. The light bulb created a drastic change in the human environment allowing a higher level of nocturnal activities. It may take some time for this to show up in genetic changes. These genetic changes, if they do occur, will not be traced to Edison having all the females. That type of evolution is more geared toward animals.

 

If you look at the pace of brain child output, it is accelerating. Culture and education are playing a role, but it also may be genetic changes in the brain that allow this brain child population explosion. Look at it this way, if a herd of deer started to multiply like crazy beyond anything before, we would assume some type of genetic change. With the brain, the idea of the light bulb is not based on one gene or protein. It more complicated. Whatever genetics were involved were made to stick through education.

[Michaelangelica]

As I understand it, evolution's chief means of bringing about a change in our genetic structure is to weed out the chaff or encourage higher reproductive rates.

What you say implies a moral, ethical or 'judgemental' attitude (not quite the right word sorry).

 

It may be that we are all evolving to be similar to those in power like dopey NY bankers and President Bush.

 

Evolution makes no judgements.

[HydrogenBond]

If we base evolution on reproduction rates, does that imply poor people are more evolved since they reproduce more? Christ did say blessed are the poor. Does than mean he was the original person to come up with the correlation for humans? I am just pocking fun at the human equals animal assumption for evolution.

 

I am not saying this is true, but it may be a historical possibility. The reproduction assumption may have been a result of repressed desire, in compensation for the strictness of the Victorian times. It may have been sort of a wish forfillment, allowing the kings of science to go at it. They may have seen themselves leading the herd because of their evolved brains. It could have started out as a pick-up line. If it works keep using it, until finally it was carved into stone, with the original motivation lost to time.