Evolved

[the tree]

Something that's been bugging me...

Once an animal is intelligent to be selective about its mate, major changes will happen over fewer generations.

...true or false?

 

Also, why do some animals find things attractive that don't appear to have any real benifit? Like those birds with massive red air sacks under thier beaks wich are more of a liability than anything else, can't remember what they're called.

[PhDP]

Once an animal is intelligent to be selective about its mate, major changes will happen over fewer generations.

 

I don't see why. Humans are much smarter than drosophila, but they can change much faster than we do, probably in part because they have a relatively simple design. Also, you don't need to "know" why you are selecting a mate, in fact, even with our great intelligence, we often don't even know why we are choosing a mate over another.

 

Also, why do some animals find things attractive that don't appear to have any real benifit? Like those birds with massive red air sacks under thier beaks wich are more of a liability than anything else, can't remember what they're called.

 

It can be because of sexual selection. Even if a trait reduce survival, let say by 5% because it's useless or even because it's attracting predators, it can be favoured by time if it's attracting 10% more females. Sexual selection can play against natural selection and do very strange morphological transformation.

[Sisyphus]

There are at least two reasons I can think of.

 

One, something like the air sack might be a way of demonstrating healthiness and available resources. "Look at me. I can have this big, colorful frivolous thing hanging off me. I can afford to waste resources."

 

And two, an instinctive attraction to something doesn't just go away as soon as the survival value of that thing does. Say, hypothetically, there is a plague of deadly vampire bats that attack monkeys on the back of the neck. It lasts a long time, and those monkeys who evolve neck spikes to keep them away have a much better chance of survival, and thus, necks spikes become instinctively attractive in a mate, since they show a greater probabillity that the mate will survive to bear and take care of the young. Then the vampire bats go extinct. The neck spikes no longer help individuals survive. Yet monkeys of the opposite sex are still attracted to them, and so those monkeys with the spikes have more offspring, and the spikes grow bigger and bigger until they're a hindrance.

 

......or just think humans and large breasts. When was the last time a child in a developed nation died because his mother couldn't produce enough milk?