No two individuals are identical?

(Original post by Sweetpeasw)
So going through the snap revise videos, and have reached Classification and evolution... she's just said 'no two individuals are identical'... this has confused me.
what about identical twins, or organisms which clone themselves? they're genetically identical, so by default they are identical, right?

(Original post by Flying Cookie)
I think that list is intended to outline the specific train of thought underpinning Darwin's theory.

In that context, referring to sexually reproducing organisms with inherent mixing of genes at each generation, "no two individuals are identical". In the context of individuals making choices and acting out their genetic predispositions in their potentially separate environments, the results may also not be "identical" even in mammalian "twins".

Assessing identity between organisms at a genetic or otherwise level is in itself not a straightforward task. E.g. we may be considered identical because we are the same species, so genetically you and I are identical in a way that you and a chimp wouldn't be. Many of these distinctions are made rather arbitrarily and can be very overlapping and confusing.

So the statement that two individuals are identical or not in a specific evolutionary sense, for the purpose of talking about their differences and how they play a role in evolution, is not an absolute claim. It is context dependent. There are many other angles, not just Darwin's.

For example, even in the realm of simple maths, a statement like "1 - 2 contains two numbers" only applies in a whole number range. Add a decimal point and that becomes 11 numbers (1.0, 1.1., etc.) so getting that context right is essential.

Biology especially is very sensitive to context and language! Fun fun fun