• Question: To what extent do theories of evolution support the evidence of life on other planets?

    Asked by felizadam to Adam, Catherine, Karen, Leila, Nazim on 15 Mar 2012. This question was also asked by jollyjones, fishofdoom.
    • Photo: Catherine Rix

      Catherine Rix answered on 13 Mar 2012:

      The theory of evolution explains how living things can adapt to survive in their environments through natural selection (certain characteristics make survival more likely, and if you survive you can pass these characteristics to your offspring). I think this suggests that if there is life on other planets it will be adapted to the environment on that planet. Many planets are unlikely to be able to support life though as the conditions are too harsh.

    • Photo: Leila Battison

      Leila Battison answered on 13 Mar 2012:

      Darwin’s theory of evolution explains how creatures on earth can change their shape to be the best for what they are doing or where they are living.

      But the theory of evolution doesn’t tell us exactly how life got started in the first place, and Darwin was a bit puzzled by this. But if we are looking for life on other planets, we would be looking for the shapes and behaviour of living things that would be suited to that planet’s environment.

      So if we were looking for life on Mars, it would have to be able to cope with the dry cold conditions with lots of radiation from the sun. The only things that we have on earth that can survive conditions like that are bacteria, so people are looking for things that look like bacteria on Mars. The same goes for most of the planets in our solar system, but there are hundreds of planets around other stars that will have very different conditions on them, where alien life might look very different.

    • Photo: Adam Stevens

      Adam Stevens answered on 13 Mar 2012:

      Well, for a start, there is no evidence for life on other planets at the moment. All we know so far is that there might be liquid water (which is necessary for life) on places other than Earth, like deep in Mars’ crust, or under the ice of Europa.

      Like Leila says, evolution doesn’t tell us how life started. If we assume it started the same way we think it did on Earth, then it would have probably followed a similar path right at the beginning.

      Since Mars was probably a lot more like Earth about the time life started emerging, then it’s possible if life /did/ start there, it would look exactly the same as the early life on Earth.

      But gradually Mars changed and the selection pressures that drove the evolution of these beasties would have been very different to those on Earth.

      So when we look for life on other planets we start by looking for things that Earth life needs – water, nutrients, and if we ever find anything it may look similar to life on Earth, but most likely it will look very different.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 15 Mar 2012:

      I’m not sure that the theory of evolution says anything about how likely life is to occur. That means it doesn’t have anything to say on how likely life is on other planets.

      But like the others have said, if life does start then evolution says that life will adapt to its conditions. So if we go to a planet that isn’t exactly like Earth, we should keep an open mind on where to look for life. It is only very recently that we have confirmed there is ice underneath the surface of Mars in many places. I suppose there is a tiny chance life still does exists there and we haven’t been quite looking in the right places.

    • Photo: Karen Masters

      Karen Masters answered on 18 Mar 2012:

      We have no evidence of life on other planets.

      But if it did exist I think we’d think it looked quite different to life here because it evolved totally separately.

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