Evolution Question

[Cogman]

So I read in my biology book that ant eaters evolved a longer snout to get food easier. Thats fine and dandy, but how did that happen? Did the ant eaters just suddenly decide that longer noses where more attractive and started breading exclusively with the longer noses?

I can't see it that one day they just had a kid and *BAM* he has a long nose and so do the rest of them. What I know about genetics says that should be a gradual process. But what I'm not getting is what would influance an animal to make such a change.

Another would be the fact that we don't have tails. How did that work? did a group of monkeys eventually decide that shorter tails where more attractive?

Do you see what I'm asking? Im interested in the mechanics behind what makes a thing evolve rather then whether or not there is evolution.

 

[CycloWizard]

I'll go with what I'm most familiar with first, but let me know if it doesn't make sense and I'll go from there.

Genetic algorithms are essentially man's effort to mimic natural evolution to optimally solve complex problems. There are two basic ideas that are determine whether the creature will survive or perish:
1. Genotype - this gives the properties of the critter in a given generation based on its genetic makeup. These are the independent variables in optimization.
2. Phenotype - how "good" the given genotype is in its environment (i.e. does the genotype give it properties that make it survivable/able to reproduce?). This is called a "cost function" in optimization.

To analyze the relationship between these things and determine the genotypes of the offspring and next generation, the following algorithm is used:
1. The cost function is evaluated for each child of the present generation based on its genotype (i.e. f(x)=some value)
2. Children with higher f(x) values (i.e. an animal that is "more fit" in some sense) have a higher probability of mating than those with lower fitness
3. The genotype of this generation's kids is determined by combining the genotypes of their parents in some fashion
4. Random mutations are introduced at some arbitrary rate (increases population diversity)
5. Rinse and repeat for the next generation

This seems like a very arbitrary algorithm, but it's amazing how effective it is even with naive methods for mating, mutation, and so on. Very rapid improvements in the fitness of each subsequent generations are almost always observed, then taper off after a number of generations. Another characteristic is that multiple optimal children can be obtained in this way, which is analagous to the development of multiple species evolving side by side in the same place. Yet another idea is that the fitness function might vary with time or from place to place, since obviously things that help you survive/mate in Antarctica are not very helpful in the Sahara desert. Anyway, enough rambling for now.

 

[A5]

In the anteater example, the process is pretty simple - The anteater with the longer snout is able to get deeper in the anthill, which means more food that the others can't get, which means they either live (slightly) longer or are more fit to mate. While there may only be one extra long-snouted anteater at first, it only has to survive one extra mating season over the others for the long snout to begin it's march toward the inevitable victory.

 

[Onceler]

what about mating passing on the mutation,it seems to me that most animals would sense one that is different and attack

 

[Aluvus]

Originally posted by: A5
In the anteater example, the process is pretty simple - The anteater with the longer snout is able to get deeper in the anthill, which means more food that the others can't get, which means they either live (slightly) longer or are more fit to mate. While there may only be one extra long-snouted anteater at first, it only has to survive one extra mating season over the others for the long snout to begin it's march toward the inevitable victory.

This. Additionally, in the event of a food shortage the advantage can be amplified.

As for tails: having a tail means having more tissue to support (which in turn means consuming more calories in a day). If that tail can't "pull its own weight" by, for instance, making it easier to acquire food, then it is advantageous to not have the tail.

None of the animals concerned "decided" that longer noses or shorter tails were better. The animals with those traits simply outlived or outbred the rest.

Originally posted by: Onceler
what about mating passing on the mutation,it seems to me that most animals would sense one that is different and attack

When you see a human being with a slightly larger nose than yours, is your first impulse to physically attack them?

 

[Peter]

It goes in small steps. Every newborn has random genetic mutations, some are useful, some are irrelevant, some are a disadvantage.

If such a random mutation has an advantage in everyday life, it'll be passed on - not the least because the more successful hunters are healthier, and are also more attractive to the opposite sex.

So, in our example, during an ant shortage, while all the averagely nosed ant-eaters went "NOES! WE IS OUT OF ANTS!" and starved, the ones with the extra long noses and tongues got to the food the others couldn't reach, stayed healthy and got the girl as well ... with a fat chance that the non-starved girls were of a similar genetic variety.

 

[Navid]

Originally posted by: Aluvus
When you see a human being with a slightly larger nose than yours, is your first impulse to physically attack them?

Quit that.
You make me laugh uncontrollably.

 

[frostedflakes]

Originally posted by: A5
In the anteater example, the process is pretty simple - The anteater with the longer snout is able to get deeper in the anthill, which means more food that the others can't get, which means they either live (slightly) longer or are more fit to mate. While there may only be one extra long-snouted anteater at first, it only has to survive one extra mating season over the others for the long snout to begin it's march toward the inevitable victory.

Exactly. And it probably would have been a subtle change, it's not like in a generation or two their snouts went from short to long. It probably would've happened over hundreds (thousands?) of generations.

 

[dorion]

Originally posted by: frostedflakes

Originally posted by: A5
In the anteater example, the process is pretty simple - The anteater with the longer snout is able to get deeper in the anthill, which means more food that the others can't get, which means they either live (slightly) longer or are more fit to mate. While there may only be one extra long-snouted anteater at first, it only has to survive one extra mating season over the others for the long snout to begin it's march toward the inevitable victory.

Exactly. And it probably would have been a subtle change, it's not like in a generation or two their snouts went from short to long. It probably would've happened over hundreds (thousands?) of generations.

Yep and who says there's only one long snout progenitor. If the population is large multiple long snouts can pop up across the population, the different long snouts could even use different genes to get the same effect. The different genes then have a chance to make even longer snouts if their holders mate and the genes cooperate.

 

[Gibsons]

Another consideration is how long something like this might take. Anteater generation time is apparently about two years Text
Just to throw some numbers out there: figure the average nose length of the population gets just 1% longer each generation. That's slow enough to where we humans might not even notice it in our lifetime. Then take 1,000 years or 500 generations (not a very long time really). If you started with a 1 inch long nose, it would be about 144 inches after 1,000 years... (I just did 1.01^500)

 

[PlasmaBomb]

Thats a really long nose...

 

[Pulsar]

Building on plasma's comment (That's a really long nose)....

One wonders that if size DOES matter, why we aren't evolving a specific set of equipment that's just a touch..... larger.....

I swear, my curiosity is only highly technical.

 

[Gibsons]

Originally posted by: Pulsar
Building on plasma's comment (That's a really long nose)....

One wonders that if size DOES matter, why we aren't evolving a specific set of equipment that's just a touch..... larger.....

I swear, my curiosity is only highly technical.

I'll suggest that the selection might not be as strong as you think. There are many other factors which may influence reproductive success.

Also, if it is happening, it's happening at a rate that's very difficult to notice in a human lifetime. 1% per generation would be about 1% per 20-25 years in humans.

 

[Onceler]

Originally posted by: Onceler
what about mating passing on the mutation,it seems to me that most animals would sense one that is different and attack

When you see a human being with a slightly larger nose than yours, is your first impulse to physically attack them?[/quote]

No I wouldn't attack someone,but animals in the wild will attack the one that has a percieved difference to the others

 

[elmer92413]

Originally posted by: Gibsons

Originally posted by: Pulsar
Building on plasma's comment (That's a really long nose)....

One wonders that if size DOES matter, why we aren't evolving a specific set of equipment that's just a touch..... larger.....

I swear, my curiosity is only highly technical.

I'll suggest that the selection might not be as strong as you think. There are many other factors which may influence reproductive success.

Also, if it is happening, it's happening at a rate that's very difficult to notice in a human lifetime. 1% per generation would be about 1% per 20-25 years in humans.

My own theory on this:
Europeans < Africans
Clothes > Clothes
In order for something like that to be passed on the ability to see it would be a factor. And warmer climates are where people tend to wear less. I would love to see if the hard data holds this up.

 

[dorion]

Originally posted by: Onceler

Originally posted by: Onceler
what about mating passing on the mutation,it seems to me that most animals would sense one that is different and attack

When you see a human being with a slightly larger nose than yours, is your first impulse to physically attack them?

No I wouldn't attack someone,but animals in the wild will attack the one that has a percieved difference to the others

But its so gradual that by the time "normals" notice, the mutation has spread to a large part of the population, especially if it is beneficial.