Friday, December 14, 2007

Dyslexic (Dyspraxic) Birds

What are the genetic basis of language? Mutations of the gene FOXP2 cause developmental verbal dyspraxia (DVD), a speech and language disorder that compromises the fluent production of words and the correct use and comprehension of grammar. But is FOXP2 role in audio communication a human innovation?

It seems not. Sebastian Haesler and collegues in Berlin have tried to suppress FOXP2 function in live zebra finchs , a cute Australian bird that is often used for study on learning. Male zebra finchs, in fact, learn their song from their parents.

The image above, from the Haesler paper, shows that the birds lacking FOXP2 function are much less accurate in imitating their parent's song. While the controls' spectrograms nearly perfectly match those of their tutors, FOXP2 defective birds struggle to imitate them but with evidently poor results. Most strikingly, the defects are similar to those of children born without a properly functional FOXP2 gene.

What does it mean? The neuromolecular basis of language are not a human innovation: they are shared by birds and humans. The same gene controls speech/song learning and production in both species nervous system. This means, amazingly, that the basis for speech-like audio communication were laid before the split between Synapsida (mammalians and extinct "mammalian-like" reptiles) and Sauropsida (other reptiles, including birds). It must have been some reptile-like amphibian in the moist forests of Carboniferous, more than 330 millions of years ago, to first emit the progenitor of both birdsongs and human songs.

Full open access paper on PLoS Biology, where you can also listen the normal and FOXP2-impaired zebra finch songs!

Sunday, December 9, 2007

Communicating with the enemy

Being a prey is always hard; being a toxic prey is somehow better, but you have to warn your enemies you are not a good deal. How do you do it? Toxic or otherwise harmful animals display colourful visual signals that mean "don't eat me, or you will regret it". Predators at first may not know the meaning of the signal, but after their first encounter, they will learn to avoid the colourful but toxic ones, and the other preys will be saved. But how did this kind of signaling evolve? Why some species evolve it, and some else not?

Analyzing the evolution of the caterpillars of the butterflies Papilio , Kathleen D. Prudic and coworkers discovered that the evolution of such signals is most influenced by the visual background on which the caterpillar preferibly is found. Caterpillars eating herbs or other narrow-leaved plants independently evolved warning signals for predators, while the ones eating on trees and other plants with large leafs did not. That is, warning signals evolve where there are consistent backgrounds that make it easier for the predator to recognize them and learn, while on complex environments like trees such visual clues could take a while to be recognized by predators, making the strategy inefficient.

Full open access article on PNAS

Monday, December 3, 2007

Earth-mass planets detected by 2011?

Good news everyone. The systemic blog reports exciting developments for exoplanets addicted (like me). New exoplanets detection rate is now as high as one planet per week. And there is more. If the extrapolation above holds, it means that we will be routinely detecting Earth-size planets around nearby stars by 2011-2012. I wonder when we will begin to detect moons of these critters.