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Evolution and Gravity Update
ByA reader writes:
Uh, no. Your original commenter had it closer to right. I got lots of nice degrees so I'm going to call this one, sorry.
"Gravity" isn't a law -- that is "stuff falls" doesn't quite cut it. There is a "law of gravity" or more precisely a "law of universal gravitation" which can be expressed mathematically, basically saying, that there's a force between two objects proportional to the products of constants associated with each object (their "gravitational masses"), divided by the square of the distance between their "centers of mass". _That's_ the law. And you don't really do much to prove it when you drop a penny to the floor unless you have super-super-bitchin' measuring devices. Mostly (not entirely) it's been proven by astronomical observations, also with something called a torsion balance: go Google it.
"Evolution" doesn't have a law because there's just not a nice mathematical expression of it to call a law.
No matter how well you back up the theory -- and lots and lots and lots of us no have been in labs doing biochemical directed evolution experiments so it's backed up -- it ain't going to be a "law," because I can come along and ask you, so what's the law? and all you can do is go, "uhh....uhhh...y'know, evolution." It's a complicated set of ideas not (yet, if ever) describable as a set of equations. Indeed, as originally described, or commonly described in those science textbooks, it's also wrong. Bacteria, for example, can undergo some types of Lamarckian evolution -- the giraffe stretches its neck -- under conditions of nutrient starvation or infection with viruses. And as Stephen Jay Gould and others pointed out it's not quite right to separate environment and genetics the way the theory of natural selection invites us to. But there's a core set of ideas -- a theory -- about variation and selection and randomness, and it's well validated. It can't (at least now) be a "law" no matter what you get in a lab: but it may well have more datapoints then, say, universal gravitation.
