Effects of the earth's mass on evolution?

[shlegminitism]

Here's a question, though I'm not sure if it is suited to the biology section, since it might overlap physics and Earth science. Hell, i don't know; I'm an English major
Forgive me if i make any foolish assumptions.

To what extent has the Earth's mass affected the types of life that have formed?

If the Earth were 20% larger (or smaller), but was formed under the same circumstances, same habitable climate, etc., would things be very different than they are now?

Just wondering how significant the Earth's mass was to all of this. I guess I'm assuming that if the mass was larger, gravity would exert a stronger pull and we might just have beefier legs? I'm also assuming that life (those first tiny single and mult-icellular critters) came to be and evolved in a way that was ideal in relation to the mass of this planet, and that if the mass were different, then other critters would have come to be that are slightly different, but similar in function. Any Idears?

 

[Simon Bridge]

Welcome to PF;

It kinda depends on what you mean by "different".
Usually if you change something significantly (and 20% more mass would be significant) it will have a big effect, even to the extent of making life impossible on Earth. However, evolution is something that happens on the scale of the entire Universe.

Basically, if life had evolved on an Earth-like world with higher gravity (but other things also modified so life is not excluded) then you would expect to see adaptations for the higher gravity.

Which adaptations?
Depends on the assumptions - look at the burgess shale fossils to see what kind of biodiversity is possible just with shelled creatures that have jointed legs.

A land animal with legs would need to have thick legs - yes - and stronger lungs. A human-oid would share features with an elephant.

The more you make things besides the mass the same, the more the same the expected evolutionary outcome.

I'm wondering if this belongs in science fiction?

 

[Evo]

It's another unaswerable "what if" thread. We could do this 24/7.