Common descent?

Question

What do scientists/evolutionists believe was the common ancestor from which everything evolved?

Answer 1

Well I hope you aren't expecting an answer like 'the horseshoe crab'.

It is going to be the smallest possible thing that has DNA and can survive and reproduce. It would be something like a bacterium.

The actual original ancestor is almost certainly not around anymore. For the same reason that you can't buy a Model T from Ford. Later models were much more efficient, and drove the earlier ones to extinction.

Answer 2

It is not known what the common ancestor of everything is. We can only go so far back as smaller, more basic forms of life leave little to no remains after several million years.

When it comes to things in science, there's no "believing". There's hypothesising or postulating but ultimately no one claims they have the end-all answer.

Answer 3

there are various ideas there. common descent is well established for verterbrates, pretty well established for animals and plants, eukaryotes maybe. bacteria and especially viruses are another story. perhaps there was no single common ancestor, instead a community of early life forms existed that swapped genes a lot.

see for instance:

http://www.sciencemag.org/cgi/content/abstract/284/5423/2124