It ought to be so simple, right? Planet of the Apes and all that. From Colin Barras at BBC:
It is true that, today, some researchers have a well-thought-through idea of what the LCA looked like and how it behaved. The trouble is that other researchers have equally well-reasoned models that suggest an LCA that looked and behaved in a completely different way. And that puts the research community in a bit of a quandary.
In principle, fossilised remains of the LCA might come to light any time. They might even be discovered this very year. But because there is so little agreement on what the LCA should look like, researchers will interpret the fossils differently.
“It’s a problem that we might encounter,” says Almécija. “Are we going to be able to recognise the LCA when we find it?” More.
The trouble is, in that case, we don’t know what we are looking for and thus cannot be sure if we find it.
See also: Does the evidence point to mankind’s fully natural origin ?
The search for our earliest ancestors: signals in the noise