Are we related?

Scientists like to know the full story. Usually this is all about knowing things to the nth degree. But with some disciplines, like biology and geology, it is also about knowing how things have changed over time.

Now “a beginning, a muddle and an end” may well be Philip Larkin’s idea for the classic plot of a novel, but it isn’t a plot that scientists are comfortable with in their professional life. A good example of a story like this is the missing link type of story, such as the linking-animal between the other apes and homo sapiens. This isn’t the only example of this sort of story, and they are particularly enticing because, like that last piece of the jig-saw, everything else is already in place which makes the missing bit even more perplexing.

In a similar vein scientists have also puzzled over the continuum between simple and complex animals. We are obviously an example of a complex animal. For example, we have a highly developed nervous systems which allows us to process stimula from our environment so we can for instance…..watch TV, and shop. There are also some nice examples of simple organisms, like sponges. It would be nice to be able to fill in all the stages between these extremes. Scientists have thought that organisms like the marine worms, xenoturbella and acoelomorpha, might fit in to this area; they don’t have a fully developed nervous system or gut for example, but they still out-complex sponges.

Sometimes simplicity is enough!

There is an intuitive feeling that complexity is something that organisms develop in to, and simplicity is something that we develop from. This sounds fair enough, otherwise you end up with the crazy situation when something has gone through a lot of development just to be simple! Now while this may be intuitively right it isn’t always correct. Scientists working on the xenoturbella and acoelomorpha at University College London and Universite de Montreal have found that there are occasions when ‘the crazy situation’ is what actually happens.

The DNA of these worms have been sequenced and analysed using mathematical techniques to infer their evolutionary history. It turns out that neither of the worms is primitive, and in fact share a common ancestor with complex lifeforms, like us.

In effect the worms are evolving backwards. This sounds like a bit of a waste of development but then again nature isn’t trying to impress anyone and maintain funding. The bottom line is survival. If an organism can find a niche that doesn’t require complexity then complexity is redundant and the organism may lose it.

It’s a surprising outcome, but it does make evolutionary sense. And it is seen elsewhere as well. My cat just lays in bed all day, occasionally soaking up a bit of milk. It too has found it’s niche, and is now evolving back into a sponge!

See the original article at Lowly marine worms distantly related to humans.