h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I still maintain we are evolving, but it is happening slowly and we can't see it. But things like us getting taller and our little toes getting smaller are happening and are evolution in progress so you can't really say 'this is it' this is where the human race stops and doesn't change anymore. Species either die out when the environment changes or adapt to suit the new environment. We are an adaptable species and the environment is changing, we *will* change along with it even if it takes millenia.

The getting taller is not necessarily an evolutionary change - it is likely due to better diet when we're young.

As for the little toe shrinking (and wisdom teeth disappearing, etc.) perhaps there is something else at work there. It can't be evolution, because those characteristics do not result in a reproductive advantage to the individual. Or, rather, it could be evolution, but by a different means than natural selection. Perhaps, when there in an environmental pressure, certain mutations spring up spontaneously in several places, leading to more individuals with that characteristic.

Naive, patronising ("primitive"?), and not very clearly thought out.

We ARE still apes, by any normal definition of "ape".

We have definitely NOT managed to arrest the process of evolution, in ourselves or anything else.

We (as a species) are most definitely NOT monogamous, much as many of us vow to be and pretend to be (I've often said that if right wing bigots are looking for an unnatural sexual practice to be prejudiced against, the most unnatural one that human practice is monogamy. Funny, almost none of the anti-homosexual Christians I've pointed this out to have agreed with me...)

And finally, evolution does not happen to organisms in isolation, it is a process of response to environmental pressures. There is talk here of people mutating to become resistant to UV radiation. Agreed, it's not a hugely useful trait in modern day England, perhaps, so if it arose it wouldn't be much of an advantage - but if we continue depleting ozone like we have been doing, UV tolerance is going to become a survival trait which WILL be selected for. Impressed as this entry is with our technological advances, we haven't yet reached the stage where we are completely independent of our environment.

Evolution continues: some individuals survive and reproduce, some do not. Traits exhibited by the reproducers proliferate, traits exhibited by the non-reproducers die out.

Evolution is NOT the deliberate selection of "better" characteristics, which is aiming for some possible perfection which you think it has now reached. This is a very human-chauvinist view of it, often due to a misinterpretation of the phrase "survival of the fittest". It doesn't mean "fittest" by any measure we would be able to quantify in isolation. It just means "able to survive". One might just as well say "survival of the survivors" - it means the same thing.

Evolution is the continual testing of species against their environment, whatever that environment is, and the result of their reproductive success or failure.

The environment for modern man is quite different than that of his forebears - but we're still reproducing, or failing to, in response to it. Given that in secular countries with proper sex education, the general trend is to smaller families and the use of contraception, evolution in the western world is currently selecting for uneducated and/or religious people. Not a pleasant prospect, really... but then what do I care? I'm not having kids. Which also illustrates my point.

H.

One other point:

evolution never stops. As long as a species exists and is reproducing, it is evolving by definition. Some organisms reach an equilibrium with their environment, and do not exhibit any major changes even after millions of years - sharks, for example, haven't changed much for hundreds of millions of years. Others get in an evolutionary arms race with other species or with specific aspects of their environment, and change rapidly - horses have emerged from small, many toed cat size things in only a few tens of millions of years.

But the point is, if you look at any organism over a short period - say a merely million years - you'll most probably struggle to spot any changes at all. Evolution simply doesn't work that fast with complex organisms like ourselves. But make no mistake - it's happening.

H.

Thanks for your post, H.

A couple of points, as I remember them from your posts:

Regarding "fittest": I was very careful NOT to infer that fitter meant better. It simply means better able to produce offspring, whether through better health (and hence longer survival and more time for reproduction), or through better reproductive success (i.e. more attractive to potential mates, hence more mates; or, more fertile, etc). Reread the article and point out to me where I imply that evolution leads to "better" humans.

Reproduction does NOT mean evolution by definition. For evolution to occur, the organism must change. Sharks are not much different because they have not evolved much (because they are well suited to their environment). And for a whole species to evolve, all of the individuals must change in the same way. After all, it is the shared characteristics that group individuals together into a distinct species. There will always be individual within the species that have this or that characteristic that is different from the rest, but unless that characteristic spreads through the whole species, it is not an evolutionary change for the species.

Yes, we are still subject to the forces of evolution, but since there is no way for genetic changes to spread through the species, the species can not evolve.

And I fully recognize the time periods involved.

Um, there was other stuff I wanted to comment on but can't remember now.

GL, you said:
"Yes, we are still subject to the forces of evolution, but since there is no way for genetic changes to spread through the species, the species can not evolve."

A catastrophic change in environment can cause extinction of all the organisms that do not have the mutated characteristic that permits survival. The surviving organisms then have no choice but to pass the mutation on. I see evolution as more of a process of elimination of poor traits for any given environment rather than selection of improved traits.

You're absolutely right, Witty. And should there be a catastrophic change, humans will again evolve.

I guess there are two types of evolution, aren't there - the slow and steady one, and the response to catastrophic change one. My argument really just applies to the slow and steady kind.

Hooloovoo - went back and got the points of yours I wanted to reply to:

"Naive, patronising ("primitive"?), and not very clearly thought out."
Ouch! Some beginning.
Naive - possibly
patronising - no, I must disagree. I was referring to societies where natural selection can take place - i.e. where people who do not have some advantageous characteristic can indeed die and hence that characteristic can spread through the population. Thus it requires a primitive society without an advanced medical practice. Plus it requires a society where the rate of reproduction is not checked by cultural practices. Again, so that a new advantageous characteristic can spread.
not very clearly thought out - well, we'll see.

"We ARE still apes, by any normal definition of "ape"."
We are talking of evolution of species here. Last time I looked, Apes and Humans were different species.

"We have definitely NOT managed to arrest the process of evolution, in ourselves or anything else."
Evidence, please. Simply denying my premise does not constitute a refutation.

"We (as a species) are most definitely NOT monogamous"
Possibly. But we also don't reproduce to our capacity, which is what's required for natural selection to work. Natural selection selects those who reproduce more, but if everyone just produces their 2.3 children, then any reproductive advantage of a new characteristic is not expressed and hence doesn't spread species-wide.

"...but if we continue depleting ozone like we have been doing, UV tolerance is going to become a survival trait which WILL be selected for."
But how? Let's say that trait arises in an individual at the time when the ozone is depleted. How will it be selected for? How will that individual produce more offspring than the rest of humanity? The people without that trait may get skin cancer and cataracts and some of them may die early because of it. But virtually all of them will still have their 2.3 children. And so will the individual with the new trait. His advantage is not realized.

Okay, I've been trolling on the internet and found some good information.

First, it appears that natural selection isn't the only mechanism for evolution. There is also random genetic drift. The idea here, is that the frequency of a certain characteristic may "drift" a little in the next generation, due to sampling error. For instance, say a characteristic occurs with a probability of 0.5 in a population. Since there are relatively few offspring, the frequency in the next generation may be 0.49 or 0.51. Subsequent generations may drift farther until the probability is either 0.0 or 1.0 after which no further drift is possible. Some types of catastrophic change also fit into this mechanism.

Here's a link for an article on current evolutionary thinking:
http://www.talkorigins.org/faqs/modern-synthesis.html

And here's a link about Random Genetic Drift:
http://www.talkorigins.org/faqs/genetic-drift.html

I think my arguments still stand with regards to natural selection, but they do not take into account random genetic drift.

OK, point by point...

Sorry about the sharp start! Bad day.

Naive - possibly. OK.

Patronising - I still think so. You're saying some people on earth are subject to evolution and some aren't. It's a bit Nietzschean, don't you think? Plus, are there ANY societies now with no access to advanced medical practice? Whether or not they choose to use it, and whether it is sufficiently financed by their government or others is a separate question. Is there any society anywhere which is so cut off that it has no access to, say, antibiotics? (seriously curious, I think the answer is no but I'm ready to be corrected)

"Last time I looked, Apes and Humans were different species."

Last time *I* looked, "ape" was not a species. There are *several* species of apes: gibbons, orangutans, gorillas, chimpanzees, bonobos and humans. We're all apes - the definition of which is "any of various primates in which the tail is very short or absent".

""We have definitely NOT managed to arrest the process of evolution, in ourselves or anything else."
Evidence, please. Simply denying my premise does not constitute a refutation."

Extraordinary claims require extraordinary evidence. You're the one making the extraordinary claim, not me. Do you have evidence that evolution of humans has halted?

I contend that you've misunderstood the nature of evolution to an extent, which is why you're making this observation. My evidence for that is your own arguments.

"But we also don't reproduce to our capacity, which is what's required for natural selection to work."

Nonsense. Natural selection will work perfectly well on ANY reproducing species. If the species produces fewer adults with each successive generation, it will die out - natural selection. If it produces more adults with each generation, it will either outstrip its food supply or be culled by predation - natural selection again, with the less suitable survivors weeded out. Note that this happens even if each mating pair produces on average only 2.1 adults. The only effect of more reproduction is that outstripping of the food supply or predatory culling happens sooner.

"Natural selection selects those who reproduce more"

No, it doesn't. It doesn't work like that. It REJECTS those who reproduce less, or not at all, for whatever reason. This is a critical distinction to make, because your wording implies some kind of purpose to natural selection which is simply not present.

"but if everyone just produces their 2.3 children, then any reproductive advantage of a new characteristic is not expressed and hence doesn't spread species-wide."

You've a bit of a clue in that bit - how does a couple produce 2.3 children? Obviously, they don't. Some couples produce 2, some produce 3, and crucially, some produce ten and others none at all. Your 2.3 is just an average - but some traits are steadily rejected, every generation.

You're also far too demanding expecting that a particular trait be species wide - there's too much variation across a species to be that blinkered. For instance, a wonderful example of evolution in action is the hereditary condition known as sickle cell anaemia. It does not affect Caucasians, as far as I know, but causes illness and death in later life for people of African origin. How can such a condition survive natural selection? Surely all the suffers would have been "selected out" thousands of years ago? Well, no, because there's a silver lining to the cloud. Sickle cell anaemia sufferers have dramatically increased resistance to malaria - so they are more likely to reach reproductive age than their non-sickle cell peers. A situation unique to a relatively small section of the human species, but natural selection at work, no doubt. In this modern era of malaria remedies it's hard to say whether sickle cell anaemia will eventually die out. What do you think?

Here's a statistic for you. The success rate for human in vitro fertilisation recently overtook the natural method. In other words, statistically it is now *easier* to conceive by artificial methods (i.e. test tube babies) than it is by normal sexual reproduction. So all the couples who in previous generations would have produced no offspring at all, are now in a position to produce two, or three, or more children. Put that together with the increasing tendency of the affluent and the educated not to have children at all, or to have smaller families than average, and the implications for near-future evolution are interesting...

As for how UV resistant traits will be selected for - use a little imagination. If it's going to become an issue, it's not going to be one for perhaps fifty or a hundred years. By that time, if a trait expresses itself among a tiny minority of the population and they gain immunity to UV damage as a result, what do you think every parent with a dollar to spare is going to do? They're going to make damn sure THEIR kid (if they have one) is engineered to have that gene so they don't die of skin cancer at 35. Selection. It might not be "natural", by the normal definition, but it'll be selection nevertheless. And that means evolution.

In fact, far from human evolution coming to a halt, we are on the brink of an unprecedented event in the history of life on earth - within our lifetimes, we may see the beginning of a vastly *accelerated* evolution of humankind, but an evolution unlike any that has gone before. This evolution will be governed not by natural selection, but instead be *directed*, intentionally, by the very organisms on which it operates - ourselves. Let's hope we get it right, eh?

H.

OK, point by point...

Sorry about the sharp start! Bad day.

Naive - possibly. OK.

Patronising - I still think so. You're saying some people on earth are subject to evolution and some aren't. It's a bit Nietzschean, don't you think? Plus, are there ANY societies now with no access to advanced medical practice? Whether or not they choose to use it, and whether it is sufficiently financed by their government or others is a separate question. Is there any society anywhere which is so cut off that it has no access to, say, antibiotics? (seriously curious, I think the answer is no but I'm ready to be corrected)

"Last time I looked, Apes and Humans were different species."

Last time *I* looked, "ape" was not a species. There are *several* species of apes: gibbons, orangutans, gorillas, chimpanzees, bonobos and humans. We're all apes - the definition of which is "any of various primates in which the tail is very short or absent".

""We have definitely NOT managed to arrest the process of evolution, in ourselves or anything else."
Evidence, please. Simply denying my premise does not constitute a refutation."

Extraordinary claims require extraordinary evidence. You're the one making the extraordinary claim, not me. Do you have evidence that evolution of humans has halted?

I contend that you've misunderstood the nature of evolution to an extent, which is why you're making this observation. My evidence for that is your own arguments.

"But we also don't reproduce to our capacity, which is what's required for natural selection to work."

Nonsense. Natural selection will work perfectly well on ANY reproducing species. If the species produces fewer adults with each successive generation, it will die out - natural selection. If it produces more adults with each generation, it will either outstrip its food supply or be culled by predation - natural selection again, with the less suitable survivors weeded out. Note that this happens even if each mating pair produces on average only 2.1 adults. The only effect of more reproduction is that outstripping of the food supply or predatory culling happens sooner.

"Natural selection selects those who reproduce more"

No, it doesn't. It doesn't work like that. It REJECTS those who reproduce less, or not at all, for whatever reason. This is a critical distinction to make, because your wording implies some kind of purpose to natural selection which is simply not present.

"but if everyone just produces their 2.3 children, then any reproductive advantage of a new characteristic is not expressed and hence doesn't spread species-wide."

You've a bit of a clue in that bit - how does a couple produce 2.3 children? Obviously, they don't. Some couples produce 2, some produce 3, and crucially, some produce ten and others none at all. Your 2.3 is just an average - but some traits are steadily rejected, every generation.

You're also far too demanding expecting that a particular trait be species wide - there's too much variation across a species to be that blinkered. For instance, a wonderful example of evolution in action is the hereditary condition known as sickle cell anaemia. It does not affect Caucasians, as far as I know, but causes illness and death in later life for people of African origin. How can such a condition survive natural selection? Surely all the suffers would have been "selected out" thousands of years ago? Well, no, because there's a silver lining to the cloud. Sickle cell anaemia sufferers have dramatically increased resistance to malaria - so they are more likely to reach reproductive age than their non-sickle cell peers. A situation unique to a relatively small section of the human species, but natural selection at work, no doubt. In this modern era of malaria remedies it's hard to say whether sickle cell anaemia will eventually die out. What do you think?

Here's a statistic for you. The success rate for human in vitro fertilisation recently overtook the natural method. In other words, statistically it is now *easier* to conceive by artificial methods (i.e. test tube babies) than it is by normal sexual reproduction. So all the couples who in previous generations would have produced no offspring at all, are now in a position to produce two, or three, or more children. Put that together with the increasing tendency of the affluent and the educated not to have children at all, or to have smaller families than average, and the implications for near-future evolution are interesting...

As for how UV resistant traits will be selected for - use a little imagination. If it's going to become an issue, it's not going to be one for perhaps fifty or a hundred years. By that time, if a trait expresses itself among a tiny minority of the population and they gain immunity to UV damage as a result, what do you think every parent with a dollar to spare is going to do? They're going to make damn sure THEIR kid (if they have one) is engineered to have that gene so they don't die of skin cancer at 35. Selection. It might not be "natural", by the normal definition, but it'll be selection nevertheless. And that means evolution.

In fact, far from human evolution coming to a halt, we are on the brink of an unprecedented event in the history of life on earth - within our lifetimes, we may see the beginning of a vastly *accelerated* evolution of humankind, but an evolution unlike any that has gone before. This evolution will be governed not by natural selection, but instead be *directed*, intentionally, by the very organisms on which it operates - ourselves. Let's hope we get it right, eh?

H.

From your second reference:

"Studies of evolution at the molecular level have provided strong support for drift as a major mechanism of evolution. Observed mutations at the level of gene are mostly neutral and not subject to selection."

Given that genetic drift is inevitable upshot of the biochemistry of reproduction, there is no way to stop it. The first sentence above implies that it is a major mechanism of evolution. So even if there is NO natural OR directed selection, evolution cannot be stopped by any means at all!



H.

Ah, GL. Your argument is slightly disingenuous. As Hoovooloo points out, you *can't* average out the birth rate, since averages mathematically obliterate the differences between numbers, and observing evolution is all about observing differences. So if the Smiths have 3 children and the Joneses have 2, then the Smiths are ahead of the game (at least for one generation) even though the average is 2.5.

To head you off at the next obvious argument, you could say that the birth rate will average out over time, and that in the next generation the Smiths will have 2 children while the Joneses have 3. But in order for that to be true, you need to assume that evolution has in fact stopped, making the proof of your argument a cute little rhetorical trick, that, calling it "your argument" rely on the condition it is trying to prove - a circular argument.

Granted you conceded the point about catastrophic change, but that is a very real thing and we are living with it now. HIV is wiping out a significant portion of the population in Africa, and it will have a marked effect on the genetics of an entire continent. Exactly what that change will be is impossible to say, and that leads me to my next point - since we all die within our own lifetimes (or at the end of them, if you insist on being accurate ) without exception, it makes observing our own evolution extremely difficult. All we can do is look backward and point out differences in our little toes and wisdom teeth that can be attributed to random drift. We can't know what changes in our bodies will become significant until after they become significant, and that might not happen for a long, long time.

And then you say "our medical advances mean that I don't have to have a large family in order to ensure the survival of a few of them." But GL, THAT IS EVOLUTION! Think about it - the humans who have advanced medicine are more likely to survive. You might discount "medical advances" as not being related to our genetics, but that's where you get slightly disingenuous again. Medical advances are certainly a product of our intellect and the distrubition of the benefits of the advances is determined by changes in human behavior patterns (economic and governmental structures). Animal intellect and behavior are clearly linked to heredity. If over the course of hundreds or thousands of years some civilizations collapse while others thrive, it is evidence that the thriving cultures have adapted in some way, and if those adaptations are technological or behavioral they are as valid a part of evolution as are useless body parts dropping off.

In other words, 35-SPF sunscreen is evidence of evolution. The ape with the sunscreen *already* can tolerate more UV radiation.

What a great discussion! Even if I do seem to be losing the argument. But I'm not quite dead yet.

Okay, I agree that my original statement is wrong - we ARE still evolving, through the mechanism of Random Genetic Drift (which I didn't know about until I found that web site)(and which also includes the catastrophic change mechanism). However, I still maintain that we are not evolving anymore through natural selection.

Part of our differences may be due to what I consider evolution. I've tried to explain before, but I think I haven't been clear. For me, humans evolved when, say, they went from Homo Ergaster to Homo Erectus (side note: just had to look up those terms - here's the reference: http://www.handprint.com/LS/ANC/evol.html#chart). There is a clear biological difference between the two hominids. Erectus has clearly evolved from Ergaster and is a different creature. Now, there is lots of variation within the species and these are pockets of evolution in progress, but until the new characteristics become part of the definition of the species, I don't consider the species as a whole to have evolved.

So, my thought is that since humans are now so far removed from the life and death struggles with their environment (and so far removed from natural processes) that are neccessary for one group of humans to supplant another, it is now impossible for the human species to evolve through natural selection. In other words, if natural selection was the only mechanism for evolution (which it isn't, I now know), then in 1,000,000 years, we would still be homo sapiens.

Now, I'll reply to the individual points you've both made in another post.

Patronising - still no. There was no value judgement involved - I was simply referring to a group that is still subject to natural processes and hence still subject to selection. Primitive doesn't mean better or worse. As for whether such groups actually exist any more - I don't know. Perhaps in the Amazon basin?

Human/Ape species - in this reference they clearly talk as if Apes and Humans are two different species:
http://www.talkorigins.org/faqs/mom/momevol.html
And here's the definition of Ape from the online Miriam-Webster dictionary:
"1 a : MONKEY; especially : one of the larger tailless or short-tailed Old World forms b : any of two families (Pongidae and Hylobatidae) of large tailless semierect primates (as the chimpanzee, gorilla, orangutan, or gibbon) -- called also anthropoid, anthropoid ape". Note that it doesn't include humans in the definition.
Also, here is the definition from Encarta:
http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761556424
Same story - Apes and Humans are not the same species. Or rather, humans are not included in the group of species referred to by the term "ape".

Next point: my comment about reproducing to capacity as being neccessary for natural selection. This is needed so that small variations in reproductability (if that's a word) can have an effect. If a new trait gives me a small reproductive advantage, but I only produce 2 or 3 children like everyone else, then there is no way that they will die out and my progeny will eventually take over.

You also mention outstripping food supply or predation as parts of natural selection. Quite correct. And man has largely removed himself from both of those.

Distinction between reproducing more or reproducing less. Same difference. I don't see how "reproducing more" implies some purpose. Reproducing more is a way to bring a trait *into* the genome, while reproducing less is a way to eliminate unsuccessful traits. Both are part of natural selection and neither implies any purpose - it is just a process.

species-wide being too demanding. Well, why is that too demanding? After all, we are talking about the evolution of the species, aren't we? Yes there is evolution via selection going on in pockets, but in 1,000,000 years, that won't matter - the species as a whole won't have evolved (via selection). And even the sicle cell thing - man is there again removing himself from the selection process via modern medicine. Natural selection gave rise to the condition, but modern medicine is/will arrest that process. Hence, another example of "no more selection".

Your points about future man-made evolution, through genetic manipulation are well taken and I agree. However, my argument is just about natural selection (and getting further pared down all the time ).

And now on to d'E's points:

regarding averaging out the birth rates. It's not necessary for my argument. The fact is that we choose to have a limited number of kids, whether we have a reproductive advantage or not. Thus the advantage is not, um, taken advantage of. And hence doesn't result in a gradual rise in occurance of the new characteristic.

Regarding HIV - that is a good example of the catastrophic change cause of evolution (like the plant example in that reference). A cause which fits into the Random Genetic Drift mechanism and which I totally ignored.

Regarding medical and social advances as evolutionary change. I must differ with you here. I think traits that are not coded into our genetics are not evolutionary changes. The organism hasn't changed, only it's behaviour, which can just as easily change back. I haven't argued this point very well, but I've just run out of time. I'll be away until next Monday (the 24th), so don't be dismayed if I don't reply to anything for a while.

And thanks, both of you, for taking the time here. Just out of curiosity, Hoovooloo, how did you find this article? It was written as a result of a discussion at the Atelier (it was too long to just post it there and might have gotten lost in the backlog). Do you lurk there?

Patronising: I think I'll agree to disagree on that. I think it could be interpreted that way, but if you didn't mean it, fine. You're not patronising ME, after all.

Ape: hmm. I don't much trust a dictionary that begins its definition of "ape" with the word "monkey". And saying humans are not apes is like saying humans are not animals. Of course we're not animals, we're people! Except of course we ARE animals. And what type of animal are we? Well, genetically, by descent, and in appearance and in many behaviours, we fit the description of an ape. If it's got feathers, webbed feet, and a bill, and it quacks like a duck, isn't it a duck?

"but I only produce 2 or 3 children like everyone else": where on earth do you get this idea that everyone is producing 2 or 3 children? Have ever MET a Catholic?

Man has removed himself from outstripping food supply has he? Tell that to the populations of several southern African countries.

The distinction between selection of those who reproduce more and rejection of those who reproduce less is just a way of getting away from the linguistic implication of purpose to evolution.

Species wide is too demanding because you appear to have a very narrow view of the definition of a "species". You seem to demand that a "species" be a completely homogeneous group, with a consistent set of genetic characteristics and physical features. The human race barely fits that description now. ALL that is required for some definitions of the word "species" is for two individuals to be able to breed successfully. ANYTHING which prevents that is sometimes held up as an example of speciation, EVEN if the "species" are physically and genetically very similar and are only prevented from breeding by some physical barrier, like, say, an ocean.

The definition of a "species" is a very tricky one, because humans like to put things in neat categories defined by definite events. We deal very badly with continuums and processes, and life and the universe has an annoying habit of existing as a bunch of processes operating across various continuums. Example: most people would be happy defining lions and tigers as separate species. But they can interbreed successfully, and the only thing stopping them is the Indian Ocean. Are they the same species? Well, yes and no. They're genetically similar enough, but they're also obviously very different. This is a manifestation of the Sorites paradox.

On my left, I have a pile of beans. There's maybe a thousand of them. On my right, I have just one - no pile, just a single bean. I add a bean. So now I have a pair of beans. It's not a pile yet, is it? But how many do I have to have before it constitutes a pile? Twenty? A hundred? The answer is, there is no answer, because the word "pile" is too vague. We have a feel for what it is, and we also don't mind much that it's vague. However, for some reason, we DO mind that the word "species" is vague. But you CAN'T be precise about something like that, sorry. Another example: film a tadpole in a tank. 24 frames a second for six weeks. At the end of it there's frog and long roll of film. Now, there's a tadpole in frame one, and there's a frog in the last frame. So - point to the last frame with a tadpole in it, and the frame next to it where I can see a frog. You can't, because it's a continuum. And species are like that. Some are better defined than others, but they are like that.

And finally, I don't lurk the Atelier - I just went to the stats page http://www.bbc.co.uk/h2g2/guide/info and saw the entry title under "Most Recent Entries". And since this very week my University Project on Evolution vs. Creation was on the front page (plug, plug) A730522 it caught my eye.

Thanks for an entertaining discussion!

H.

Blimey o riley!
As a race we are evolving, but are we all evolving in the same way? Way back when the "fish" creature went to live in different places and evolved differently and bacame as diverse as shrimp and whale. Today we have Africans with a tendancy to Sickle Cell Anemia (sp?) but almost an immunity to skin cancer, we Europeans have no sickle cell problems but are prone to cancer. And there are other examples that I can't be bothered to go and look up - things like the Asians have more body hair and the Orientals have very little body hair.
Given this, and given that although there are some peoples who are mixing up the various gene pools, there are still many groups of humans who could perhaps evolve differently because they keep the gene pool unaffected / undiluted.
Before anyone accuses me of being racist, I'm not saying there is any better or worse scenario, but is it possible that there will eventually be differnt varieties of human, in the same way there are different varities of monkey or cat?

That's not racist FATC, and there are *already* humans who are almost as different as many so-called "separate" species. If an alien biologist came to earth with no concept of political correctness, he () might well find several "species" of human. And even by our definition, he might be right. This tells us nothing about humans, and everything about our definition of the word "species".

H.

I know you are away GL, but if I have understood you correctly you would accept a radical change (a change from one 'species' to an other as evolution, but not anything less than that)? Would you accept, though, that humans are still changing?

I mean, would you count, for example, the interbreeding of racial groups to the extent that everyone was a uniform shade of milk chocolate (or whatever), with charateristics from all groups appearing in various proportions as an evolutionary change or just a change? That wouldn't be a result of natural selection through birth rate, but in some way would involve the genetic manipulation of the species without bothering the scientists.

I should probably check those other links now...

GL: It's all very well to say that selection favours people who have more offspring, but it only selects that mutated gene if those offspring actually survive to reproductive age and manage to pass it on...if someone had 20 children but they all died in infancy, the new gene would not be passed on at all.

Have you read any Richard Dawkins, btw? If not, (and I have the feeling you haven't ) please do. I think you'd enjoy his writing.