Natural selection, nature kills the weakest

[silenzer]

As I understand evolution, with natural selection, nature kills the weakest, for an example predators killing the slowest in a herd of Antilopes.
What I don't understand is how life could have evolved into something as complex as us in only 2.5 billion years. I've heard of epigenetics, but that doesn't transfer from one generation to another does it?
To narrow it down, what I don't understand is how 2.5 billion years could have offered such vast possibilities in an organism? If we say the life span of all creatures is ~5 years (bacteria having the lowest lifespan), 2.5 billion/5 is 500 million, and 500 million times all creatures that have ever lived... that is a huge number, I know, but I just don't think it matches the complexity of a human organism.
I saw an example of a bird on a tiny island with a small beak evolving into a bird with a longer beak. How is this possible? There are millions, millions, millions of variations an organism can change in, and one out of a thousand birds decides to have a slightly bigger beak, and once that bird has become dominant someone develops an even longer beak and so on until the bird has reached an efficient beak. How is this possible?

Can anyone clarify this?

https://www.physicsforums.com/showthread.php?t=414876 This is an excellent example, how in hell does an organism develop this in only 2.5 billion years?
Also, our hair. If black people are our ancestors, and they have lost nearly all their hair... why did they do so? Surely it was neither beneficial nor damaging to have less hair. Why did the all change?

 

[Pythagorean]

African people aren't ancestors. We all (incluing Africans) share the same ancestor believed to be from Africa. Just like we didn't evolve from the monkeys you see today: both humans and monkeys evolved in parallel from a common primate ancestor.

 

[silenzer]

African people aren't ancestors. We all (incluing Africans) share the same ancestor believed to be from Africa. Just like we didn't evolve from the monkeys you see today: both humans and monkeys evolved in parallel from a common primate ancestor.

Alright, but why did black people lose their hair? How is it beneficial? And I'd like an answer to the other questions as well.

 

[Pythagorean]

As for hair, the reason we don't have it is because we don't need it. We have technology. So there's no survival pressure on us to have hair all over. It's not an extinct trait though; because of the freedom, we have all kinds of different degrees of hair coverage among the human population.

 

[silenzer]

As for hair, the reason we don't have it is because we don't need it. We have technology. So there's no survival pressure on us to have hair all over. It's not an extinct trait though; because of the freedom, we have all kinds of different degrees of hair coverage among the human population.

I understand what you mean. We have technology, so the hair-trat has gone floppy. Having legs has not gone floppy, because we are still largely dependent on legs.
What about the other things I asked of?

 

[Pythagorean]

As for the complexity you've already seen the answer to the question, you're just expressing your disbelief. If you can come up with a reasonable argument, then find it's flaw, then you may understand where your disbelief is at.

Also, I don't trus your numbers in the first place. You kind of hand waved some numbers in; the calculation seemed to be kind of simple for such a complex topic.

Lastly, there seems to be a bit of a snowball effect with life. It seems to get exponentially more complex with time. From single cells to community cells to multicellular to social organisms, we continue to widen the badwidth through which we transfer information laterally across a single generation rather than solely by DNA each generation.

 

[DaveC426913]

Alright, but why did black people lose their hair? How is it beneficial? And I'd like an answer to the other questions as well.

Do you mean why did humans lose their hair?

Evolution isn't direct. It is entirely possible that losing our hair was a side-effect of some other property, perhaps a disease that came and went, or a mutation that promoted lighter skin, or a change in diet. These things might have led to a higher survival rate and since loss of hair is linked to them, that might get carried along too. If a mutation is not harmful, it can be propogated.

I'm not suggesting that might be the cause for hairless primates, I'm simply pointing out that changes are often much less direct than it seems.

Another oft-cited example (for birds this time) is feathers. Proto-birds did NOT evolve feathers to fly; they evolved feathers as part of some OTHER useful trait - perhaps plumage for mating, or even earlier, a way of venting heat or insulating from cold. Gliding was a completely fortuitous, accidental side-effect of these other survival traits. It was only AFTER the feathers were fully developed evolutionarily (for plumage, cooling or heating) that their usefulness as an escape mechanism had an effect on their propogation through the species.

 

[silenzer]

As for the complexity you've already seen the answer to the question, you're just expressing your disbelief. If you can come up with a reasonable argument, then find it's flaw, then you may understand where your disbelief is at.

Also, I don't trus your numbers in the first place. You kind of hand waved some numbers in; the calculation seemed to be kind of simple for such a complex topic.

Lastly, there seems to be a bit of a snowball effect with life. It seems to get exponentially more complex with time. From single cells to community cells to multicellular to social organisms, we continue to widen the badwidth through which we transfer information laterally across a single generation rather than solely by DNA each generation.

I'm not simply expressing my disbelief, I'm asking how one out of a thousand birds can get the trait of a slightly longer beak out of billions of variations in traits in 2500 years, and the next one gets a slightly longer beak, etc.

You can trust my numbers, because they have no value. I know the possibilities are incredibly high, because 2.5 billion years divided by the average lifespan of an organism times the number of all organism that have ever lived is a huge number. What that number is exactly doesn't matter.

 

[DaveC426913]

As for hair, the reason we don't have it is because we don't need it. We have technology. So there's no survival pressure on us to have hair all over.

We have technology, so the hair-trat has gone floppy. Having legs has not gone floppy,

What are you people talking about? You think we lost our hair 100,000 years ago because of technology?

 

[silenzer]

Thanks for your answer, Dave.

Edit: Oh... my understanding has gone through the window once more :(

 

[Pythagorean]

my assumption was fire, heat, warmth, yes.

 

[DaveC426913]

I'm not simply expressing my disbelief, I'm asking how one out of a thousand birds can get the trait of a slightly longer beak out of billions of variations in traits in 2500 years, and the next one gets a slightly longer beak, etc.

You can trust my numbers, because they have no value. I know the possibilities are incredibly high, because 2.5 billion years divided by the average lifespan of an organism times the number of all organism that have ever lived is a huge number. What that number is exactly doesn't matter.

1] There is always variation in a species.
2] Oft-times the selection has nothing to do with survival. For example, long beaks may be a mating selector. That means it will rapidly proliferate through the species.

Look at height in humans. A big variance. Women go for taller men. Taller men get selected for no survival reason. Fast forward 50,000 years (and pretend we are still primitive savannah-dwellers), and humans are eating fruit from higher on the tree that bears can't reach. Or somesuch.

We look back and we assume that humans evolved height so that they could reach higher fruit. We'd be wrong.

 

[silenzer]

1] There is always variation in a species.
2] Oft-times the selection has nothing to do with survival. For example, long beaks may be a mating selector. That means it will rapidly proliferate through the species.

Oh, right! It could be a mating selector. Of course!

 

[Pythagorean]

Why would you expect them to have the exact same length? That would be impressive to me, given the nature of entropy in such energetic systems. Granted, I'm already impressed by how well life fights entropy locally.

 

[Ken Natton]

I’ve mentioned this notion before on this forum and it was questioned by other contributors. But from a fairly authoritative source, the account I heard about how we became the naked ape was all about our large brains. The large brain is a very energy hungry organ and it generates a great deal of heat. Our existing methods for losing heat were not efficient enough, and so we shed our hair and developed a profusion of sweat glands instead. So we are not just the brainiest species, we are also the sweatiest species.

Whether or not you accept that story, it is clear that clothes-wearing has nothing to do with our becoming the naked ape. We shed our hair long before we developed the habit of wearing clothes. The evidence for that is written into the DNA of the creepy crawly things that live on our bodies and in our clothes.

 

[DaveC426913]

I’ve mentioned this notion before on this forum and it was questioned by other contributors. But from a fairly authoritative source, the account I heard about how we became the naked ape was all about our large brains. The large brain is a very energy hungry organ and it generates a great deal of heat. Our existing methods for losing heat were not efficient enough, and so we shed our hair and developed a profusion of sweat glands instead. So we are not just the brainiest species, we are also the sweatiest species.

Whether or not you accept that story, it is clear that clothes-wearing has nothing to do with our becoming the naked ape. We shed our hair long before we developed the habit of wearing clothes. The evidence for that is written into the DNA of the creepy crawly things that live on our bodies and in our clothes.

Yes, though, if I interpret it correctly, the question isn't really about a specific evolution of a trait, but about what forces drive the evolution of traits. The OP is trying to figure out how randomness in beak length leads to a whole species having a long beak.

The answer is that a trait does not evolve to suit a purpose or fill a niche, a trait just happens - and, sometimes, as a side effect, some factor of the trait becomes useful, often in an unrelated way.

 

[Ygggdrasil]

To narrow it down, what I don't understand is how 2.5 billion years could have offered such vast possibilities in an organism? If we say the life span of all creatures is ~5 years (bacteria having the lowest lifespan), 2.5 billion/5 is 500 million, and 500 million times all creatures that have ever lived... that is a huge number, I know, but I just don't think it matches the complexity of a human organism.

For bacteria, your estimate of their lifespan is off by a factor of 10,000. The doubling time for a culture of bacteria is on the scale of 20 min - 1 hr.

 

[NobodySpecial]

If we say the life span of all creatures is ~5 years (bacteria having the lowest lifespan), 2.5 billion/5 is 500 million,

It's not the lifespan that matters it's the generation time - how long from being born to breeding, for an asexually reproducing bacteria this is minutes. For little creepy crawly early life it could be hours or days

one out of a thousand birds decides to have a slightly bigger beak, and once that bird has become dominant someone develops an even longer beak and so on until the bird has reached an efficient beak. How is this possible?

Because it east more and so has more and healthier babies who also have the long beak gene. Of those the ones with the slightly longer beak have more and healthier babies ...
The ones with the short beak don't eat as well and have fewer babies so the proportion of long beaks in the population rises.

If black people are our ancestors, and they have lost nearly all their hair... why did they do so? Surely it was neither beneficial nor damaging to have less hair. Why did the all change?

We evolved from apes that lived in rainforest and needed to keep warm, then we moved out onto the plains in the bright sunshine and needed to sweat more and survive in the sun. SO those with less hair and darker skin were more likely to make it to adulthood.
Then we moved north into the cold dark lands, those freaks with lighter skin were more able to synthesis vitamin D in the long dark euorpean winters and the few hairy weirdos suddenly became popular with the girls on the long winter evenings (as a way of keeping warm)

 

[DaveC426913]

For bacteria, your estimate of their lifespan is off by a factor of 10,000. The doubling time for a culture of bacteria is on the scale of 20 min - 1 hr.

Actually, it's hardly off at all. Reread what he said.

The average for life in general he pagged at 5yr. Bacteria are the the low end. Presumably tortoises and trees are at the high end.

If trees live 4000 years, and the average for all life is 5 years, then, depending on how you do your averaging, the shortest lifespan is ~5h. Not bad for a head calc.

 

[Pythagorean]

I’ve mentioned this notion before on this forum and it was questioned by other contributors. But from a fairly authoritative source, the account I heard about how we became the naked ape was all about our large brains. The large brain is a very energy hungry organ and it generates a great deal of heat. Our existing methods for losing heat were not efficient enough, and so we shed our hair and developed a profusion of sweat glands instead. So we are not just the brainiest species, we are also the sweatiest species.

But then by that logic, couldn't you argue that harrier people are dumber? I mean to say that hairiness is not an extinct trait. Don't we have all varying degrees of hairiness among humans? ...which is why I assumed it is a free trait with little impact from environmental pressure (not that I continue this belief in light of new information/arguments).

Whether or not you accept that story, it is clear that clothes-wearing has nothing to do with our becoming the naked ape. We shed our hair long before we developed the habit of wearing clothes. The evidence for that is written into the DNA of the creepy crawly things that live on our bodies and in our clothes.

What about fire and non-clothing shelter? What about climate change?

How were naked, hairless people able to survive? You would freeze to death in many regions of the world overnight wouldn't you? I guess if this all occurred in Africa before the migrations than the climate could have easily been conducive to the survival of naked, hairless sapiens. Or you could just be a really cuddly species when the sun goes down to survive the cold nights.

 

[Lievo]

I saw an example of a bird on a tiny island with a small beak evolving into a bird with a longer beak. How is this possible? There are millions, millions, millions of variations an organism can change in, and one out of a thousand birds decides to have a slightly bigger beak, and once that bird has become dominant someone develops an even longer beak and so on until the bird has reached an efficient beak. How is this possible?

What makes it fast is the fact that there is already a silent potential for this change. Let's take an (oversimplified) example:

Suppose there exists 3 genes (g1,g2,g3) that can influence the size of the beak, each one presenting 2 alleles (a1, a2).

To make things simple let's say beak size depends on the alleles according to the following formula: s=g1*g2*g3, and alleles value is either a1=1 or a2=2.

Let's begin with a population with no pressure so that each allel is equally likely. Then the size of the beak will be according to the equaly likely alleles:

1*1*1=1 (1 case out of 8)
1*1*2=2 (1 case out of 8)
1*2*1=2 (1 case out of 8)
1*2*2=4 (1 case out of 8)
2*1*1=2 (1 case out of 8)
2*1*2=4 (1 case out of 8)
2*2*1=4 (1 case out of 8)
2*2*2=8 (1 case out of 8)

so the mean size is about 3.4 (27/8) and most of the population will be in the 2-4 range.

Now suppose a selective pressure begins that strongly favorises the longest beaks, for example say that the length of the beak directly gives you the number of childrens an individual will have. At the next generation this will change the proportion of the different allel.

a1: 1+2+2+4 = 9 cases out of 27
a2: 2+4+4+8 = 18 cases out of 27

Now let's examine the phenotype of this new population:

1*1*1=1 (9+9+9 =27 cases out of 324)
1*1*2=2 (9+9+18 =36 cases out of 324)
1*2*1=2 (9+18+9 = 36 cases out of 324)
1*2*2=4 (9+18+18 = 45 cases out of 324)
2*1*1=2 (18+9+9 =36 cases out of 324)
2*1*2=4 (18+9+18 = 45 cases out of 324)
2*2*1=4 (18+18+9 = 45 cases out of 324)
2*2*2=8 (18+18+18 = 54 cases out of 324)

The mean beak size in this population is (1*27+ 2*36 +2*36 + 4*45 + 2*36 + 4*45 + 4*45 +8*54)/324= 3.75

So in a single generation, despite no single change in the nature of the gene, you can have a 10% increase in beak size.

This is basically why you can have fast adaptation: mutation will remain silent and useless for a very long time, and one day if it finds an impact on the fitness the now-interesting mutations will spread quickly and become more prevalent within the population.

 

[Borek]

As to how fast it goes:

Go to http://www.bpp.com.pl/bitozoa/bitozoa.htm

Read.

Go to http://www.bpp.com.pl/bitozoa/bitozoa-download.htm

Download, unpack, start the program.

Select options/parameters. Check "five eyes". Click Restart button.

First generation moves completely at random, around 3rd-5th generation bitozoa become quite good at getting to the food. Evolution is incredibly efficient.

 

[silenzer]

Thanks everyone!

 

[Ken Natton]

But then by that logic, couldn't you argue that harrier people are dumber? I mean to say that hairiness is not an extinct trait. Don't we have all varying degrees of hairiness among humans? ...which is why I assumed it is a free trait with little impact from environmental pressure (not that I continue this belief in light of new information/arguments).



What about fire and non-clothing shelter? What about climate change?

How were naked, hairless people able to survive? You would freeze to death in many regions of the world overnight wouldn't you? I guess if this all occurred in Africa before the migrations than the climate could have easily been conducive to the survival of naked, hairless sapiens. Or you could just be a really cuddly species when the sun goes down to survive the cold nights.

I am surprised by your line of reasoning, Pythagorean, I do not follow it at all. Firstly, according to the account I refer to, the hairy covering we had was not for insulation from cold. Counter intuitive as this may seem, it was the exact opposite. A hairy coat is as effective a protection from the heat of the sun as it is from the cold. When we rose onto our hind legs, we had less need for the hair on our back, since it was no longer turned up to the sun. Which leads to the next point that will probably be even more surprising to you: Only the hair on the top of our head is vestigial from the days when we had hair all over. The rest of it we have re-evolved for an entirely different purpose – sexual attraction. Before you fall off your seat at that assertion, you should understand that it has nothing to do with the aesthetic, only with pheremones.

As best I can remember the numbers, we became the naked ape about 200,000 years ago. We migrated out of Africa around 70,000 years ago. We became clothes wearers about 50,000 years ago.

And I certainly never equated hairlessness and intelligence. It is clear enough to me that our nomadic, tribal ancestors were every bit as intelligent as we are. We only live a much more advanced lifestyle today as the result of cumulative achievement, not because of ever increasing intelligence.

 

[Pythagorean]

I am surprised by your line of reasoning, Pythagorean, I do not follow it at all. Firstly, according to the account I refer to, the hairy covering we had was not for insulation from cold. Counter intuitive as this may seem, it was the exact opposite. A hairy coat is as effective a protection from the heat of the sun as it is from the cold. When we rose onto our hind legs, we had less need for the hair on our back, since it was no longer turned up to the sun. Which leads to the next point that will probably be even more surprising to you: Only the hair on the top of our head is vestigial from the days when we had hair all over. The rest of it we have re-evolved for an entirely different purpose – sexual attraction. Before you fall off your seat at that assertion, you should understand that it has nothing to do with the aesthetic, only with pheremones.

Well, you admit yourself that this is counterintuitive and surprising, so you might not be terribly surprised that I don't know the detailed ways human biology manifested. Regardless, I am glad to gain this insight from you. I sometimes forget about human pheromones because of the controversy attached to the commercialization of them.

As best I can remember the numbers, we became the naked ape about 200,000 years ago. We migrated out of Africa around 70,000 years ago. We became clothes wearers about 50,000 years ago.

So then this would correlate with the discovery of fire wouldn't it? 200-400 thousand years ago (maybe longer if you believe some claims). That doesn't give much time for evolution though. I'm still curious how we were able to survive the cold.

And I certainly never equated hairlessness and intelligence. It is clear enough to me that our nomadic, tribal ancestors were every bit as intelligent as we are. We only live a much more advanced lifestyle today as the result of cumulative achievement, not because of ever increasing intelligence.

No, I earnestly didn't mean to even imply that you did. I was applying your logic but with a false premise (confusing hair for shelter with hair for pheromones, concluding that people that were hairy didn't overheat because they their lineage didn't use their brain enough, finding other ways to propagate). It was a bad example, but I really wasn't thinking that you thought that.

 

[DaveC426913]

But then by that logic, couldn't you argue that harrier people are dumber? I mean to say that hairiness is not an extinct trait. Don't we have all varying degrees of hairiness among humans?

It doesn't work that way. There is no suggestion that neurons = 1/hair.

 

[Pythagorean]

It doesn't work that way. There is no suggestion that neurons = 1/hair.

That's an undue simplification of my question. To take it to the extreme, my question was:

[PLAIN]http://www.biwook.net/shared/thumbs/240-e14319e40cf0fca409700e86c08bd4ae.jpg

how does this guy not overheat unless he uses his brain less if that theory holds? But the whole point was to provoke a deeper reply from Ken to provide more context, which he did. So the question's no longer relevant. Again, it was a bad example, but it highlighted my misconception (which wasn't that neurons = x/hair ... though maybe a nonlinear equation... nevermind)

 

[DaveC426913]

That's an undue simplification of my question. To take it to the extreme, my question was:

[PLAIN]http://www.biwook.net/shared/thumbs/240-e14319e40cf0fca409700e86c08bd4ae.jpg

how does this guy not overheat unless he uses his brain less if that theory holds?

OK, let's acknowledge that this is an apocryphal example - it's not really how it works, but...

The point here is that of the few people in the population who are excessively hairy, a fraction of them will accidentally get sick from heat prostration during a particularly hot, dry summer before they can breed. That's one or two less families in the next generation that are hairy. Multiply that by 1000 generations and you will have a population that leans strongly towards lack of hair.

 

[NobodySpecial]

There is no suggestion that neurons = 1/hair.

Damn I was hoping there was.

We do still all agree that sexual attraction = 1/hair don't we ?

 

[Ken Natton]

Huh. Since my point has generated quite a bit of discussion, perhaps there are one or two other points worth making. Most of what I have said here comes from a particular edition of the BBC science series ‘Horizon’. At the time it was broadcast, a couple of years ago, I became involved in a discussion about it on another forum. One of the key points made in that discussion was that all of these changes, tree dweller to plain wanderer, mover on all fours to upright stance, growth of brain, loss of hair, changes in diet – also related to the discovery of fire, of course – and several others besides, were not something that happened in a linear sequence, but all occurred concurrently, because they were all interdependent.

I remember at the time being particularly fascinated by the point that much of the evidence about shedding hair and wearing clothes came from the DNA of lice. They too have had to evolve as our habits have changed!

Unfortunately, I cannot find any details about the edition I am talking about. But in my searches I have turned up the following Scientific American article:

http://www.scientificamerican.com/article.cfm?id=the-naked-truth-why-humans-have-no-fur

 

[DaveC426913]

We do still all agree that sexual attraction = 1/hair don't we ?

Bodily hair, but more importantly, in terms of receding hairline, yes.

 

[Ken Natton]

As best I can remember the numbers, we became the naked ape about 200,000 years ago. We migrated out of Africa around 70,000 years ago. We became clothes wearers about 50,000 years ago.

And therin lies the problem with memory. On the migration from Africa and becoming clothes wearers, my numbers are in the right order of approximation. On the becoming the naked ape I'm out by a factor of ten. We became the naked ape about 2 million years ago. So Pythogorean, that somewhat increases the period over which we survived both furless and clothesless!

 

[NobodySpecial]

. We became the naked ape about 2 million years ago. So Pythogorean, that somewhat increases the period over which we survived both furless and clothesless!

Naked and clothesless in Arica is fairly easy - try it in Scotland

 

[Pythagorean]

I guess if you assume Africa had two million years of good weather!


I've been reading the wiki on the human evolution timeline since Ken's last post. It looks like Homo Erectus is who were talking about. They were apparently the first to use fire but it's unclear when.

 

[DaveC426913]

I guess if you assume Africa had two million years of good weather!

Being a tropical country, it's a pretty safe assumption, yes.