::::::We should also remember that one of the biggest sources of gene exchange among bacteria, besides plasmids, is in fact bacteriophage viruses. They can infect one bacteria and ferry genetic material from it to another bacteria, and something like 70% of ocean-dwelling bacteria on earth today are in fact infected with a bacteriophage of some kind. So, to answer your question, PhilipN, it is possible for only one bacteria to have developed the trait, but if that bacteria was infected with a virus, as most are, those genes would have been spread to other bacteria in the vicinity, giving them the ability to reproduce sexually as well.[[User:TonyPark|TonyPark]] 12:17, 13 January 2012 (EST)
:::::"Who did it produce with?" - Your question presupposes that there had to be two distinct sexes. My following point will be an educated guess. It may not be right, but it's just an example of how the different sexes could have occured.
:::::If you take a look at flowers, you'll find that each flower has both male and female reproductive organs. This is pretty much universal over all plant species. Animals on the other hand, tend to have distinct males and females (at least, most vertebrates). This would imply that the separate reproductive organs were present before plants and animals diverged from a common ancestor. The common ancestor would likely have both pairs of organs, as plants do today. Plants, perhaps, never lost this trait. However, at some point after the divergance, animals became distinctly male and female (again, at least in vertebrates).
:::::As you know, organisms need energy, and the more body parts and organs you have, the more energy you require. Could it be that in animals, organisms in a species started to become specialised for which organs they used? In half of a population, the female rep. organs were slightly reduced, and vice versa. This would mean that the organisms required less energy. They would all still have both pairs of organs, but one would be reduced. Soon, two sexes would form, as one type of sexual organ would have been reduced/lost in each group.
:::::Again, this is not fact, merely my suggestion. Add to it if you wish, or point out how this would be wrong/unlikely. Hope this helps.
:::::--[[User:RedGoliath|RedGoliath]] 17:26, 13 January 2012 (GMT)
==Why are the (expected) countless millions of transitional fossils missing?==