Archive for ‘Evolution’

September 17, 2011

Brainy molluscs evolved nervous systems four times

External appearance, it turns out, is not a good way to identify relationships between species, especially more distant relationships. And even internal anatomical structure isn’t so good either. Studies of genomes at the molecular level are more reliable. In the latest example, it’s been found that snails and octopuses do not seem to be as closely related as previously believed, even though the two cephalopods both have relatively complex nervous systems (compared to other molluscs such as clams).

Examination of the genomes can also provide estimates of how much time elapsed since different species shared a common ancestor. Based on this, it appears that the nervous systems of snails and octopuses developed their complexity independently, as probably happened also in two other less familiar types of mollusc.

Brainy molluscs evolved nervous systems four times – New Scientist

Slimy and often sluggish they may be, but some molluscs deserve credit for their brains – which, it now appears, they managed to evolve independently, four times.

The mollusc family includes the most intelligent invertebrates on the planet: octopuses, squid and cuttlefish. Now, the latest and most sophisticated genetic analysis of their evolutionary history overturns our previous understanding of how they got so brainy.

The new findings expand a growing body of evidence that in very different groups of animals – molluscs and mammals, for instance – central nervous systems evolved not once, but several times, in parallel.

Further reading:

Mollusks evolved brains on four different occasions

Phylogenomics reveals deep molluscan relationships

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September 1, 2011

Lizard genome sequence solves a human genetic mystery

Lizard genome sequence solves a human genetic mystery – io9

The interesting finding is that a number of non-coding regions of human DNA correspond to active transposons (“jumping genes”) in the lizard DNA.

Another surprise is that the lizards have essentially the same sex chromosomes as mammals – unlike birds.

320 million years ago, mammals and reptiles reached an evolutionary parting of the ways. We’ve now sequenced a lizard genome for the first time ever, and it’s vastly different from our own…but in a few crucial ways, it’s shockingly similar.

September 1, 2011

Your brain chemistry existed before animals did

Your brain chemistry existed before animals did – New Scientist.

When wondering about the origins of our brain, don’t look to Homo sapiens, chimpanzees, fish or even worms. Many key components first appeared in single-celled organisms, long before animals, brains and even nerve cells existed. …

Choanoflagellates are aquatic organisms found in oceans and rivers around the globe. Being a single cell, they do not have nerves, yet the team found both proteins in the choanoflagellate Monosiga brevicollis, and the interaction between the two was the same as in neurons