Hi all! While studying for the final, the Crohn’s disease question reminded me of this parasite podcast from a while back. http://www.radiolab.org/story/91689-parasites/
A recent nugget in The Economist adds to the ever beleaguered conversation about GMO’s. The article relays the findings of an analysis out of Cambridge in which scientists restate the ubiquitousness of genetic recombination interplay amongst organisms vis-á-vis horizontal gene transfer. A thought provoking read when viewed through the lens of what biotechnology is trying to achieve with GMO’s; the surrounding controversy sounding something like “its just not natural.” OK now. Only. It is, kinda. The scientists, examining the transcriptomes of animals and non animals, were able to determine how many genes in an organism’s genome were due to horizontal gene transfer. Humans have 145 genes in our transcriptome that originated in another organism. Kinda plays into Richard Dawkins’ Selfish Gene idea as well. Could messing with the genome of corn be less unnatural than most people think? Insert shoulder shrug here!
In class the other day, we talked about how standing genetic variation is consistent with idea that most genetic variation is selectively neutral. After spring break we’ll talk about the rate of neutral evolution and the basis for the molecular clock. This plays into a larger theme that we keep returning to, which is the continuum between determinism and randomness among evolutionary mechanisms. Another topic that we read and talked about was the use of phylogenetic tree shape to quantify rates of diversification.
Now a new study has quantified the diversification rate across a tree of >50,000 animal species. The authors describe the meaning of their findings in the short quote that I tweeted:
then Daniel Cadena (Prof. at Universidad de los Andes, Bogota) replied:
Yes, it’s truly an amazing figure, to go along with a provocative claim.
Yes, I’ll be asking you about homology on the exam tomorrow. As the author of this Allium piece puts it… it’s a concept. But don’t worry, if you get it wrong, I won’t take it as badly as Dr. Constance Noring did.
Every time we try to grapple with a big Darwinian idea, a brand new study comes out that improves our understanding. Evolutionary biology is a dynamic field.
Last week we were talking about Darwin’s phylogenetic branching model of evolution, and the objections to it regarding the failure to include reticulation events. Then, this week, a new genome scale study of the Darwin’s Finches shows that introgression of genes among lineages AFTER speciation has occurred was common during the evolution of this iconic clade.
Last week in class, we were talking about elemental composition of the oceans and atmosphere, and the ways that biological feedbacks affect that composition and shape the environment for life. It seems that scientists keep learning about new ways in which biology feeds back on processes typically classified as earth science, with implications for the large scale patterns in evolution. Sure enough, there’s a new one in the news.
It turns out that undersea volcanoes are more active when the weight of the sea above them is lowered. This was discovered by looking at activity through the cycle of tides. But it has profound implications for variation in volcanism through glacial cycles. During glaciations, sea-level is reduced and volcanism should increase, and it’s even possible that the resulting volcanoes spewing CO2 help to end those glacial periods. Although the article doesn’t make the connection explicitly, it follows that anthropogenic warming should slow down seafloor spreading by increasing the weight of the oceans. It’s a sensitive world we live in, and this study just gives us one more feedback mechanism that defines our “pale blue dot”.
Steven Pinker’s writing is crisp and biting. He’s not always right, but damn he can weave a good argument. His recent book, Better Angels of our Nature, argued that human violence has been steadily declining over historic time. Pinker tends to explain natural phenomena as outcomes of natural selection, rather than neutral evolution or random chance. He is a proponent of evolutionary explanations for human behavior rather than arbitrary cultural ones. Because he frequently writes about the ways in which humans are subject to natural selection, Pinker has a host of intellectual enemies. In this essay, he effectively lashes out at the negative reviews of his book. The result is quite entertaining, and it provides a nice snapshot of the long-standing and still vibrant neutralist-selectionist divide. Enjoy it!