Sex? Sex? Oh, please. It's copulation.

In higher organisms, sex, gender, and copulation are all neatly tied up together such that to the less well informed (read science correspondent) they are one and the same. So when some science reporter says "Sex emerged in an ancient Scottish lake", and it turns out to be fossil fish copulating, it just sends the wrong message.  To be fair it's the headline that's wrong. The article clearly states this is about copulation. Sex is when parents of two different genotypes combine their genes in offspring, and it's much older than fish. There are algae, phytoplankton, that have sexual reproduction, and to some extent bacterial transformation might be considered a form of sexual reproduction, however, in this case, two parents only result in one offspring. TPP has a colleague in psychology who says he studies sex, but he really studies gender, where the two sexes are differentiated. That's not the case, at least not obviously, among many sexually reproducing organisms and we often use the term mating types designated by +/- signs. Then it gets really strange. Consider Ulva, sea lettuce, a green seaweed that looks like a limp leaf of lettuce. When you pick up a "frond" of Ulva, you don't know what you've got; it could be a plus, a minus, each with one set of chromosomes, or it could be a spore producer with two sets of chromosomes, all three physically identical, but parts of an alternation of generation life cycle. So let's be careful about throwing around the term "sex", besides the organism's name (Microbrachius dicki) makes for an even better joke regarding copulation.