Archive for the 'Evolution' Category
Jonathan M. at evolution news recently criticized the hypothesis of a monophyletic origin of the eyes.
The common evolutionary rationalization of this phenomenon is to posit that the gene in question had some kind of propensity for promoting the development of the respective structure. But this solution appears dubious, particularly in the case of the even more spectacular example of eye development…
In this comment at the DI blog, Casey seems bewildered by the fact that researchers can spot selection at work without knowing the exact function of the new gene:
To illustrate why I used the word “magic,” we often see that papers (which Nick would probably claim show the “origin of new genetic information”) invoke natural selection, but then:
DO NOT EVEN KNOW THE FUNCTION OF THE GENE, AND THUS HAVE NO IDEA WHAT FUNCTION WAS BEING SELECTED FOR
(For example, the following papers invoke natural selection to explain the origin of a gene whose function was at-the-time unknown, meaning they did not even know what function was being selected
Forgive me Nick, but I have trouble accepting claims of natural selection when evolutionary biologists:
(a) don’t even know the function that is being selected,
Casey meet Kimura
My nostalgic streak continues
If Eoandromeda appeared after the cnidarians, the authors argue, bilateral symmetry would have to have evolved twice — once for the cnidarians and again for the bilateral organisms that came after Eoandromeda. Far simpler is the idea that Eoandromeda evolved first (see 'Simplest solution'). "This model of animal relationships calls for the least number of origins of bilateral symmetry," says Bengtson.
Over at the DI blog we read this about a recent PLOS paper
This is a further indication, of course, that non-coding regions of the genome, previously dubbed "junk DNA," are functional.
I don't see how finding high levels of conservation for non-protein coding sequence around some, but not all, wing development genes means that all non-coding regions are functional (particularly around the key gene Wingless and Ecdysone Receptor).
It's doubtful this heroic effort has shed any light on evolution. Nor is likely that similar efforts will do so any time soon
That's a strange thing to say considering that, among other things, they identified an expansion of the family of alcohol dehydrogenase genes (via duplication):
Among the genes identified, we discovered five tandemly arranged genes similar to Alcohol dehydrogenase (Adh), which potentially represent an expansion in the Lepidoptera. Comparative studies of sequence, expression and function of these genes are necessary to shed light onto their evolutionary history and ecological importance.
I recently read this at evolution news & views
Given the sheer number of these retroviruses in our genome (literally tens of thousands), and accounting for the evidence of integration preferences and site biases which I have documented above, what are the odds of finding a handful of ERV elements which have independently inserted themselves into the same locus?
I wouldn't bet on it. If I would have identified 2 TEs in humans and chimps exactly in the same genomic locus, I would predict that the most parsimonious event would be that the original insertion was in their primate ancestor. Of course, the scenario Jon M mentions is also possible, but it is a less likely scenario, since there are tens of thousands of possibilities for a TE to insert itself within large mammalian genomes.
There are different approaches towards the concept of “teleology” and in many ways it is related to a particular view or concept of “matter” and “change”. The Scholastic approach towards matter and change are described here and here. The approach is Aristotelian by nature. Darwin had good things to say about Aristotle. From Allan Gotthelf's article "Darwin on Aristotle": Darwin in a letter to William Ogle:
"Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle."
It is safe to say that Darwin did not model his concept of natural selection from an Aristotelian or Scholastic point of view as Gotthelf points out that Darwin was familiar with Aristotle's work but his respect for him only grew after he published The Origin. Mechanistic philosophy of matter and change was prevalent during Darwin's era. Paley's watchmaker analogy was the basis for the argument from design whereby reality was like a machine composed of parts with no intrinsic relationship between them. The designs in the system (or reality) were imposed from an outside agent.
There are at least 24 different species concepts and none of them can be applied to all organisms that have ever lived (Hey, J. 2001). The Species Problem is a philosophical problem of biology that can be divided into two important questions that needs to be addressed. Before giving a proper definition of the term "species", the ontological status of the concept needs to be addressed and this is the first important question. Once the ontological status is cleared, the second question is how to adequately define the term "species" so that is can be used to properly catalogue all the different life-forms. In order to answer the first question, one needs to clarify whether the term "species" firstly refers to either individuals or classes (kinds) (1a) and secondly whether universals (classes being a kind of universal) are real or not (1b)? The Species Problem is of course relevant to biology in order to understand the process of speciation. Without a proper concept of the term species, speciation is unintelligible.
Over a six-year period, a bacterium from the genus Rickettsia swept through the whitefly population, assuring survival advantages for the whiteflies and for itself. The new research appears in the April 8 issue of Science.
“Whiteflies that have this infection have greater fitness, at least in the laboratory,” said the senior author of the study, Martha S. Hunter, a professor of entomology at the University of Arizona. “We’ll be testing whether this fitness benefit exists in the field as well.”
There's also an interesting paper here on endosymbiosis:
The recognition that mitochondria and plastids are derived from alphaproteobacterial and cyanobacterial endosymbionts, respectively, was one of the greatest advances in modern evolutionary biology. Researchers have yet however to provide detailed cell biological descriptions of how these once free-living prokaryotes were transformed into intracellular organelles.
A key area of study in this realm is elucidating the evolution of the molecular machines that control organelle protein topogenesis. Alcock et al. (Science 2010, 327 :649-650) suggest that evolutionary innovations that established the mitochondrial protein sorting system were driven by the alphaproteobacterial endosymbiont (an "insiders' perspective"). In contrast, here we argue that evolution of mitochondrial and plastid topogenesis may better be understood as an outcome of selective pressures acting on host cell chromosomes (the "outsiders' view").
I remember the last time Dawkins took a swipe at E. O. Wilson. Wilson replied:
I am used to taking the heat and in the past I turned out to be right.
Evolution News and Views has a video of Stephen Meyer arguing against Front-loading and Theistic Evolution. Hoping he might be offering an argument against Mike Gene's hypothesis, and possibly provide a way out of my dilemma (it keeps me up to all hours of the night: Mike Gene or Mike Behe? Mike Behe or Mike Gene?), I watched it.
Will this help me sort it all out?
Comments section has been closed down due to completely irrelevant discussion.