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I sometimes think even most biologists don't understand how evolution works. Especially when I read about people taking the idea of spandrels seriously. Legs d

by monochr 12y ago

I sometimes think even most biologists don't understand how evolution works. Especially when I read about people taking the idea of spandrels seriously. Legs didn't evolve "for" walking, ancestors with leg like appendages survived better than those who didn't have them in the Savannah. It didn't matter if they did that by walking, swimming, running or kicking threats and opportunities as they came along. The same is true of fists and skulls. They didn't evolve for punching, but any ancestor who threw a punch - even if by accident - and didn't have their hand broken, and anyone who received one and didn't have their skull broken had a better chance of survival that those who did. The only question is if this happened often enough to warrant the extra resources that went into strengthening the bones of the hands and skull compared to using those resources into some other area of the body.

Peaker 12y ago
Saying that "legs evolved for walking" is a completely legitimate statement. Something can be said to have evolved for a purpose -- as a short-hand for saying that random changes that helped that purpose increased fitness and were selected for by natural selection.
- monochr 12y ago
  If legs evolved for walking why are they so useful for swimming? There is a set of genes that encodes for the behavior of walking or allows us to learn it and a whole other host of adaptations from our vestibular system to the angle at which our neck connects to our skull that taken together as a whole are adaptations for walking. Each on its own has many, many other uses that have nothing to do with walking and provide benefits that have nothing to do with walking. So no, legs didn't evolve for anything. But in combination with a lot of other adaptations they make walking easier than would be the case without them.
  - Peaker 12y ago
    I agree that legs didn't actually evolve for walking exclusively. They evolved for a myriad of purposes, including walking, running, jumping, swimming, and more. The fact other parts of the body also evolved to facilitate these features is not a contradiction. Evolution is like a parallel computation looking for a local optimum. When climbing the hills of the possibility landscape, various features that exist at the top of these hills can be described as the purpose of a particular search path.

by monochr 12y ago

Peaker 12y ago

Saying that "legs evolved for walking" is a completely legitimate statement. Something can be said to have evolved for a purpose -- as a short-hand for saying that random changes that helped that purpose increased fitness and were selected for by natural selection.

monochr 12y ago
If legs evolved for walking why are they so useful for swimming? There is a set of genes that encodes for the behavior of walking or allows us to learn it and a whole other host of adaptations from our vestibular system to the angle at which our neck connects to our skull that taken together as a whole are adaptations for walking. Each on its own has many, many other uses that have nothing to do with walking and provide benefits that have nothing to do with walking. So no, legs didn't evolve for anything. But in combination with a lot of other adaptations they make walking easier than would be the case without them.
- Peaker 12y ago
  I agree that legs didn't actually evolve for walking exclusively. They evolved for a myriad of purposes, including walking, running, jumping, swimming, and more. The fact other parts of the body also evolved to facilitate these features is not a contradiction. Evolution is like a parallel computation looking for a local optimum. When climbing the hills of the possibility landscape, various features that exist at the top of these hills can be described as the purpose of a particular search path.