Have we stopped evolving?

Great Debates
1

Examples of future mankind in sci-fi, traveling back through time to visit their stupid forebears (i.e., us), are often depicted with huge heads/brains, but not much brawn.

Natural selection drives evolution by weeding out certain characteristics before they can be reproduced. My hypothesis is that man has reached a plateau - our environment can no longer weed out certain characteristics because we have take control of our environment. For instance, we don’t need to be cunning hunters anymore. In other words, we are unlikely to continue to evolve bigger heads/brains because there is nothing in our environment which selects for this anymore.

To keep this thread clear and on topic, I want to limit it to the following:

(1) No God/creationism-vs-evolution discussions. Those are perfectly good discussions (and they’re all over the SDMB already), but this thread presupposes that evolution is a fact.

(2) Implicit in this discussion is that more intelligence is a good thing. That shouldn’t be a tough sell on the SDMB.

2

More intelligence is definitely a good thing. Unfortunately, evolution doesn’t know from good and bad. Are selection pressures selecting for intelligence? Think about it. People who are more intelligent are more likely to use birth control. They’re more likely to limit the number of offspring they produce, or to choose to be childless.

The dumb shall inherit the Earth, my friend.

3

The OP and the reply I believe are both making two cardinal mistakes:
(A) Adopting an excessively simplistic idea of what intelligence is and its relationship to genetic traits.
(B) False assumptions in re long-term effects of present social patterns of their immediate society.

In re man evolving under present conditions, note that (a) most of the world does not live in comfy first world circumstances (b) even in those circumstances there will be evolution, although it may be damped or redirected. In any case, since evolution takes place on time frames rather longer than any given human society has lasted, I think it’s irrelevant.

However, you can do a search on this and find several recent threads with cogent observations already made.

However in re the idea of bigger heads/brains, I think this is a bit silly. First of all, the constraints on head, brain size are the birthing canal. That little constraint has not gone away for most of the world’s population, although for the first world it might be said to with c-sections.

Second, there are costs involved in having a brain – energy and the like. If anything removal of caloric and birth canal constraints would allow for larger head sizes. However, whether there is any pressure for larger brains is another matter since the relationship between brain size and intelligence is not direct.

4

The bigger head thing (from sci-fi, remember) was meant to be silly - I understand that there’s no consistent correlation between human brain size and human intelligence. I had considered noting the comfy 1st world/far-from-comfy 3rd world issue but decided against it.

But it’s not irrelevant to the crux of my question - I understand that such evolutionary changes may not manifest until the far future. The silly sci-fi groundwork I laid was meant to underscore this point.

5

This is actually a very good post. I find it interesting on many levels.

Since the OP mentioned us possibly evolving into creatures with large brains/small bodies, I assume the crux of the question deals with whether we will actually see physical changes as we become more intelligent.

I would like to offer up something that came to mind while reading the replies.

Firstly, since we now only use a very small portion of our brains anyway, I don’t see a human actually needing to develop a larger brain to become smarter.

Secondly and slightly off course, the smaller body may actually occur. Well, maybe not smaller but almost assuredly different. With the technology available today we artificially sustain children that nature would have removed from the gene pool. My own daughter was born with a congenital heart defect that was remedied with surgery, without which she would have only lived a few years. The question of whether this surgery should be done was a no-brainer, of course, and we didn’t hesitate at all to have it done. But, I remember noticing how this fit into the greater scheme of things. We have essentially taken natural selection out of the mix. (of course all defects cannot be fixed as such, so natural selection still does it’s dirty work, just less of it.) So, it would seem, we can expect to see a noticable difference in the human body as we evolve, or would this be de-evolving?

Thirdly, is a question within this question we can ponder. Can we safely assume that we are actually smarter than our forebearers? If we were to take some of histories greatest thinkers, bring them up to date with all technology has given us to this point, would they be less smart or more smart than our contemporary thinkers?

I would be interested to see what DaVinci, Michelangelo or Socrates could make of today’s unanswered questions. But, I would be most interested in seeing what the great Egyptian designers of the pyramids could accomplish if they had the benefit of what we know now. With their ability to grasp abstract ideas of mathematics (remember that Pi had yet to be identified) and their apparent knowledge of astronomy (the portholes through the pyramids were most probably used as some sort of astronomer’s tool and used the concepts of precession in their placement).

One would think that, if we were indeed smarter than these individuals, after several thousands of years, we would already see the large brain/small body in all of us.

6

I think there are two main possibilities, here (OK, I’m sure that there are more, but these are the two that I can think of right now)…

  1. The punctuated-equilibrium hypothesis is correct, and we’re in the middle of a long period of slow, random evolution. Thus, we wouldn’t really expect to see much change in form or function of the human body.

  2. Human society, in much of the world, has reached the point where the old rules (read rules as “evolutionary pressures”) no longer apply. It’s not necessarily the fastest, strongest, and smartest of the species who get to reproduce anymore.

This isn’t necessarily a bad thing, as it tends to increase the variation available within the species if/when it should need to recover from some major disaster that wipes out a good portion of the population. This, of course, leads back into the punctuated-equilibrium bit, except we’d be in the punctutation instead of the equilibrium…

So, no, I don’t think we’ve stopped evolving. We’re just evolving in a different direction.

7

[WAG of a theory/my own views alert!!! Proceed with caution Do not take the following statements as fact. Just my own speculation.]

Not Necesarilly. As I view everything, it seems to me that natural selection is weeding out the idiots.

Why are there STD’s?

My very, very WAG that could hold some ground later on is that STD’s is natures of killing off the dumb people. Now, I am not implying that if you have an STD you must be dumb. But let’s take a step back and view the human race as a whole.

Dumbasses don’t use protection against STD’s and they have sex with other dumbasses who don’t use protection either. Not to say that these people deserve it, a nice chunk of them are uninformed.

Nature looks at the human race through her Cold Heartless Bitch™ glasses. We are on her turf and if we fuck with her, she just might fuck back. So, on comes the STD’s. Being the cold heartless bitch that she is, nature devises a way of killing off the dumb ones and if she gets rid of some of the good ones with it, no skin off her nose.

But that’s just my WAG of a theory.

8

Umm…but if you get a STD, it’s pretty likely you’ve had sex. And without a condom. So it’s already possible you’ve reproduced. Not to mention most STD kill you off slowly if they kill you at all, so you have time to have more sex (without a condom) and possibly reproduce.

(Whereas the smart guys with condoms are not getting STD’s but also not having any accidental babies.)

A trait is only influenced by natural selection if it prevents you getting offspring into the next generation.

Nature is going to have to try harder.

9

What about the STD’s that don’t kill people off like the herpes type II virus and venerial warts. As far as I know they are not 100% effective at controlling birth either.

10

If this topic includes only traditional evolution then this does not apply, but I’ll take that chance. There are two developments that have changed the rules and so should be included in this discussion.
The first is artifical intelligence. Some experts predict that if computers continue to develop at the rate they have in the past, then in the near future (next 20 years) our brains will be surpassed in intelligence by that of computers. This may mean that we will a)live a better life b) be slaves to computers c) have outlived our usefulness.
Then there is genetic engineering. Will we create Super Humans? My bet is that if it can be done, it will be done. If we are competing with those damn computers for control, we’ll have to do it.
These two factors will have tremendous influence on the human race, some bad and some good and the beat goes on.

11

I would venture to guess that the gradual progression of the species would have stopped if not reversed (due to the fact that people with even the most horrible of genetic defects can still survive and reproduce thanks to modern science), if not for the occassion mutations that cause great increases in fitness which surely slip into the population periodically and should spread quite effectively. Thus, overall, there is still potential for a gradual increase in genetic quality. And of course there is genetic engineering. When those in power finally stop whining about the “playing God” arguement we will finally start to use this wonderful tool and it will improve the wealthy world drastically. After all, if a child wilh down syndrome is going to be taken care of all its life (and thus not allowed to die young as it would in a natural environment) and may even find someone to reproduce with, why not just make it so that the person was not born with down syndrome to begin with? The former situation is no less “playing God” than the latter is.

12

The key to understanding evolution is its relationship to the environment, we mould ourselves to it.

If the environment stopped changing then we might ( some animals have not evolved much in millions of years because there environment hasn’t ).

You could argue that people who have trouble using contraceptives are going to out breed those who do IF they end up having more kids and there kids have more etc.

You can usually only see evolution over a long period because it changes very gradually and in modern western society badly adapted people don’t usually die out so obviously.

Pre-welfare it was pretty obvious that if you had too many kids you had to live in badly cramped conditions and it was miserable.

As richard dawkins wrote in the selfish gene, people think contraception is un natural BUT so is the welfare state !

13

No, some animals have not changed because whatever changes in the evironment which have occured have not adversely effected their fitness.

Now, on to the crude social darwinism:

Which says nothing about overall fitness in an evolutionary sense. Of course, post-welfare one still lives in cramped conditions.

Nothing in modern human society is particularly “natural” – the welfare state is no more natural or unnatural than democracy.

I truly dislike the use of evolutairy langauge in political contexts, and the abuse of evolutionary analogies in the same.

14

Urban myth. Cecil says so.

15

A pioint to consider: How long can we really assume current conditions will hold even in the 1st world? We have of course temporarily reduced the significance of many survival traits, but if the world experiences a massive economic/social collapse even briefly then all the old survival traits of size, speed, intelligence, disease and heat/cold resistance etc. come back into play. A major depression/war/depression cycle such as was experinced C. WWII could very well reinforce all the same survival traits that we have needed for the last 40,000 years.
Similarly one good pandemic like Spanish 'flu or Black Plague could achieve much the same thing if onnly for one trait (disease resistance).
A human generation in the 1st world is around 20 years. These events appear to come around about every 50 years or so (IANAHistorian). If one of these events comes around only every 100 years it may well have as much effect on the course of evolution as the constant pressure our ancestors experienced. The only difference may be that any effects will be pushed forward for 5 generations.
I owe my existence to the ability of my parents and grandparents to hunt and trap food and grow crops during the '30’s depression, and there are many other people worldwide who can claim the same thing. For us at least the same survival traits that were important to our pre-human ancestors have been directly selected for in us. So the current ‘selection neutral’ situation found in the wealthy 1st world will have to continue for many years before any significant change in genetic frequencies could possibly occur.

16

I think the problem is people often think evolution has to have a physical change i.e. zebras changing to horses etc.

With humans its probably less pronounced as we tend to use technology to help us adapt i.e. we wear warm clothing if we live in a cold environment.

There are some obvious points though.

For example before spectacles people with bad eyesight had a lot rougher time of it, in that way we have used technology to help us adapt – we changed the environment.

Studies of identical twins separated at birth have shown that at least some behaviour or tendency towards that behaviour is inherited so you could say people who have a tendency not to have children die out.

Unless it’s very dramatic though, evolution works very slowly so you can only see the trend over a long period of time.

Its also a statistical science normally so you can only state general things, for example, statistically you could say that people with a college degree earn more than those without BUT this doesn’t mean there won’t be exceptions such as the car salesman versus the liberal arts teacher etc.

17

Since evolution is really just change to adapt to a changing environment, and since the environment is and always will be changing, I suspect there’ll always be evolution. Will people evolve to have bigger heads? I don’t know. But it’s impossible (or so I propose) that in a million years our genome will be completely the same as it is today.

Now, if you want to stretch the concept of evolution to include more than just the changing of our genes, i.e. the evolution of our minds and our cultures, then we are constantly evolving even now. After all, a zebra of a thousand years ago lived pretty much as one does today, since their genes haven’t changed that drastically. But humans on the other hand live very differently today. And we live differently because our environment has changed and we’ve adapted to it. (and our adaptation causes our environment to change again, continuing the cycle.)

18

We’ll continue to evolve, but it’s impossible to predict HOW we will evolve because we don’t know how the environment we are adapting to will change. Are there going to be programs restricting who can breed? Will the idea of personal wealth exist in the future? Is medical technology going to allow us to grow our embryos outside the body and thus override the birth-canal limit on brain size? Are we going to colonize space? Or are we going to revert to a primitive hunter-gatherer society? Any of these possibilities would have a big effect on how we evolve.

I don’t think intelligence is as useful as it used to be. Human absolute brain size has gone down 11% in the last 35,000 years, 8% in the last 10,000. We peaked about 90,000 years ago.

19

Social Darwinism

I don’t think there is a problem in describing life in darwinian terms as its true.

This does NOT mean I support a policy or political program based on darwinian theory, what is does not have to be.

If you are good at making babies you will outbreed people who are bad at these things, thats a fact, not social theory.

Money does limit the number of kids you plan to have unless you are on welfare.

This is also a fact.

Here in the UK it is now pretty evident that many middle class asians who came into the country have done amazingly well despite arriving with virtually no money.

This is because they are smart, value education and invest in there childrens future.

These factors have meant they have moved up the social scale at an amazingly fast pace, out doing those who are either not smart or do not value education or there childrens future.

I am sure this has happened in America and here ( Germans set up most of the banks in London ) with various waves of immigration but for obvious reasons it is easier to spot with Asians.
IQ has a large hereditary factor ( see tests of identical twins who were raised apart ), this again is FACT.

BUT that does not mean we should not invest heavily in public schooling in deprived areas or ensure that people have a decent place to live.

Altering our society so its a better place to live IS an option.

20

I think there was a study of a bird population where the number of birds didn’t really alter BUT through research they found that only about 10% of any one generation actually bred.

I am not sure if i really buy into this idea that we are descended from hunter gatherer society, i think we are descended from our parents generation, we are the product of those who did well ‘then’ and kids now are the product of people who are doing well ‘now’.

As IQ does help you get money and money does help with having kids then we could be becoming smarter BUT really its the money and how you spend it that makes a difference, we are probably just turning into a breed of people who are ‘good’ at getting money - or borrowing it from the bank !

I don’t think there is anything wrong with that as getting money is the same now as a lion hunting in the wild, there is no welfare in the wild, if you don’t catch it you starve.

I know all this sounds really ruthless BUT i ain’t saying what SHOULD be, just what is !