evolution
evolgen | June 5, 2006No, Dr. Mayr did not dislike the beach. That's just how all the kids are saying, "You ain't down with the shit I'm doing." Anyway, read this post attacking the physicists for calling us stamp collectors on a blog with a very cumbersome name. MissPrism puts a throw-away link at the end of the post to Roger Lewin's 1982 interview with Mayr (available here if you have a subscription to JSTOR). I actually like MissPrism's post better than Lewin's article, so you're not missing much if you can't get access to the Mayr interview. I have some quotes from Mayr, and my responses, below the fold.
Both…
razib | June 3, 2006There has been a long standing debate in evolution of the possibility of sympatric speciation, that is, speciation between two coterminous populations. Well, here is evidence from some fish of it happening, at least in the first stages, so that genetic differentiation is minimal to non-existent. I don't know how common sympatry is, but I've been to other talks pointing to similar phenomena in other taxa, so I think there has been a detection bias toward allopatry.
But anyway, species concepts are a bugger. The main point is that population differentiation need not always be…
evolgen | June 3, 2006This post is a bitch-fest. Don't read any further if you have no interest in hearing me complain. The only reason I'm posting this is because I figure some of the people who read this blog find themselves in the same boat as me.
This summer, I will be attending the Society for the Study of Evolution annual meeting for the first time. I figured the meeting is in Long Island, New York so I may as well check it out when it's in my neck of the woods (last year it was in Alaska and next year it will be in New Zealand). The Evolution Meeting has a reputation of being less work and more play than…
pharyngula | June 3, 2006Since Evolgen recognizes the importance of evo-devo, I'll return the favor: bioinformatics is going to be critical to the evo-devo research program, which to date has emphasized the "devo" part with much work on model systems, but is going to put increasing demands on comparative molecular information from genomics and bioinformatics to fulfill the promise of the "evo" part. I'm sitting on a plane flying east, and to pass the time I've been reading a very nice review of the concept of modularity in evo-devo by Paula Mabee (also a fish developmental biologist, and also working in a small…
razib | June 2, 2006Possible ancestral structure in human populations:
Using sequence data from the Environmental Genome Project, we find strong evidence for ancient admixture in both a European and a West African population (p ~ 10^{-7}), with contributions to the modern gene pool of at least 5%. While Neanderthals form an obvious archaic source population candidate in Europe, there is not yet a clear source population candidate in West Africa.
5% isn't jack, but, that's enough to introduce lots of novel alleles which might reshape the larger population into which admixture results in introgression. Remember…
razib | June 2, 2006Some people have wondered if there is any point in signing petitions. Well, sometimes it is important to declare you exist, to stand and be counted. With all due respect to Ed, evolution's connection with "Culture Wars" is not a good thing, and, more importantly (to me) it saps genuine discourse on this topic that engages the science instead of focusing on meta-politics which will never go anywhere. There are many things in the world to be "against," and I would not say that Intelligent Design/Creationism is the most important, but, comments like this are fucking scary. On this blog I get…
razib | May 31, 2006The title is tongue in cheek, some researchers now are suggesting that speciation may be proportional to a particular energetic value. R.A. Fisher wanted an "ideal gas law" for evolutionary genetics, but this is ridiculous! In any case, one issue that many of us who are interested in paleoanthropology will have noted is that Africa seems to have been the repeated mother of hominid species. That is, "erectus" left around 2 million years ago, only to be swept aside by moderns around 50,000 years ago. Why Africa twice? This might be part of the answer, and is a flip to WIlliam H. Calvin's…
razib | May 31, 2006This lion research is just cool. Hey, I'm human, I'm a sucker for cats, and the bigger the better:
Understanding the phylogeographic processes affecting endangered species is crucial both to interpreting their evolutionary history and to the establishment of conservation strategies. Lions provide a key opportunity to explore such processes; however, a lack of genetic diversity and shortage of suitable samples has until now hindered such investigation. We used mitochondrial control region DNA (mtDNA) sequences to investigate the phylogeographic history of modern lions, using samples from…
pharyngula | May 31, 2006Fellow scienceblogger Evolgen has seen the light—evo-devo is wonderful. He's attending a meeting and listening to some of the bigwigs in the field talk about their work, in particular some research on the evolution of gene regulation. While noting that this is clearly important stuff, he also mentions some of the bickering going on about the relative importance of changes in cis regulatory elements (CREs) vs. trans acting elements, transcription factors. I've got a longer write-up of the subject, but if you don't want to read all of that, the issue is about where the cool stuff in the…
razib | May 31, 2006The American Journal of Human Genetics has a paper in its pre-print section titled "A geographically explicit genetic model of worldwide human settlement history." I quickly skimmed it (and uploaded it into the GNXP forum). I have serious issues some of the inferences made in regards to the "obvious" fit of such coalescence data with a particular demographic history. I am convinced that meta-population dynamics tend to be ignored (in part because they are just another complication) even though they can also explain the data. Nevertheless, this jumped out at me:
We further neglected key…
loom | May 29, 2006Usually when you hear about the rapid evolution of bacteria, the story is typically some grim tale of antibiotic resistance or the emergence of some pathogen once restricted to animals. Here's a nicer narrative, but no less instructive. In tomorrow's New York Times I have an article about yogurt, and how the bacteria in its culture have been undergoing drastic genomic change since the stuff was invented some 5000 years ago.
I report on a new study on Lactobacillus bulgaricus, found in many yogurt cultures. (The paper comes out some time this week in PNAS.) The analysis, based on the microbe's…
pharyngula | May 26, 2006
One of the most evocative creatures of the Cambrian is Anomalocaris, an arthropod with a pair of prominent, articulated appendages at the front of its head. Those things are called great appendages, and they were thought to be unique to certain groups of arthropods that are now extinct. A while back, I reported on a study of pycnogonids, the sea spiders, that appeared to show that that might not be the case: on the basis of neural organization and innervation, that study showed that the way pycnogonid chelifores (a pair of large, fang-like structures at the front of the head) were innervated…
pharyngula | May 26, 2006
I'm going to introduce you to either a fascinating question or a throbbing headache in evolution, depending on how interested you are in peculiar details of arthropod anatomy (Mrs Tilton may have just perked up, but the rest of you may resume napping). The issue is tagmosis.
The evolutionary foundation for the organization of many animal body plans is segmental—we are made of rings of similar stuff, repeated over and over again along our body length. That's sufficient to make a creature like a tapeworm or a leech (well, almost—leeches have sophisticated specializations), but there are…
loom | May 25, 2006If you're in the neighborhood of Woods Hole, Mass., let me invite you to my talk on Friday, June 9 at the Marine Biological Laboratory. I'll be talking about human evolution, but given that I'll be at the Marine Biological Laboratory, I figure I'll include some discussion of the marine biology in our past.
The talk is at 7 at the Lillie Auditorium, and it's free and open to the public. Directions are here.
cmooney | May 24, 2006...and since then have recommended it to my audiences at two public speeches. Randy Olson's documentary is funny, humane, and completely spot-on when it comes to the blind spots of scientists, the would-be defenders of evolution who often don't have a clue about how to connect with the rest of America. Olson inspires all of us to ask questions like these: How could the smartest people on earth actually be so bad at political communication and strategy? And when are scientists going to wake up and realize that part of the blame for the spread of anti-evolutionism in the US falls on their…
oracknows | May 24, 2006One annoying thing about the blogosphere for someone like me is that a lot of things that I want to write about pop up during the day, when I'm at work. Blogging is all about immediacy and time. Wait too long to write about a topic, and the moment's passed. For me, by the time I get home in the evening, even though someone may have e-mailed me an article that they thought I'd like to comment on, I often find myself refraining from jumping into the fray, simply because so many have already commented on it already. This problem is magnified (for me, at least) by belonging to ScienceBlogs,…
pharyngula | May 23, 2006
I just learned (via John Lynch) about a paper on cetacean limbs that combines developmental biology and paleontology, and makes a lovely argument about the mechanisms behind the evolution of whale morphology. It is an analysis of the molecular determinants of limb formation in modern dolphins, coupled to a comparison of fossil whale limbs, and a reasonable inference about the pattern of change that was responsible for their evolution.
One important point I'd like to make is that even though what we see in the morphology is a pattern of loss—whale hindlimbs show a historical progression over…
loom | May 22, 2006In tomorrow's New York Times I have an article about the origin of species--or rather, blocking the origin of species. The evolution of a new species can be a drawn out process, taking thousands or millions of years. First populations begin to diverge from each other. Later, those populations may become divided by significant reproductive barriers. Even after those populations have evolved into separate species, they may still be able to produce hybrids in the right conditions. In some cases, those hybrids may remain rare and the two species will remain intact. In other cases, the species…
jlynch | May 22, 2006 What does Sonic Hedgehog on the left have to do with whale evolution? Nothing. However a soon-to-be-published study will argue that the gene Sonic Hedgehog (Shh) played a part. The abstract reads:
Among mammals, modern cetaceans (whales, dolphins, and porpoises) are unusual in the absence of hind limbs. However, cetacean embryos do initiate hind-limb bud development. In dolphins, the bud arrests and degenerates around the fifth gestational week. Initial limb outgrowth in amniotes is maintained by two signaling centers, the apical ectodermal ridge (AER) and the zone of polarizing activity (…
pharyngula | May 22, 2006
I'm going to briefly summarize an interesting new article on cnidarian Hox genes…unfortunately, it requires a bit of background to put it in context, so bear with me for a moment.
First you need to understand what Hox genes are. They are transcription factors that use a particular DNA binding motif (called a homeobox), and they are found in clusters and expressed colinearly. What that means is that you find the Hox genes that are essential for specifying positional information along the length of the body in a group on a chromosome, and they are organized in order on the chromosome in the…