The evolutionary history of mammals can be reviewed as the evolutionary history of tooth loss. The early mammals had many teeth, and every now and then in evolutionary time, a tooth is lost wiht subsequent species arriving from that n-1 toothed form having that smaller number of teeth. With ver few exceptions, no mammals have added a tooth during the history of mammals. (Excepting maybe the very very earliest period, but probably not.)
Well, the loss of enamel itself is also an evolutionary trend in mammal history, and recent research published in PLoS Genetic associates genetic changes over time with what is known of the morphological evolution of mammals.
Continue reading Evolutionary enamel loss linked to molecular decay of enamel-specific gene
Natural Selection is the key creative force in evolution. Natural selection, together with specific histories of populations (species) and adaptations, is responsible for the design of organisms. Most people have some idea of what Natural Selection is. However, it is easy to make conceptual errors when thinking about this important force of nature. One way to improve how we think about a concept like this is to carefully exam its formal definition.
In this post, we will do the following:
- Discuss historical and contextual aspects of the term “Natural Selection” in order to make clear exactly what it might mean (and not mean).
Provide what I feel is the best exact set of terms to use for these “three conditions,” because the words one uses are very important (there are probably some wrong ways to do it one would like to avoid).
- Discuss why the terms should be put in a certain order (for pedagogical reasons, mainly) and how they relate and don’t related to each other.
When you are done reading this post you should be able to:
- Make erudite and opaque comments to creationists that will get you points with your web friends.
- Write really tricky Multiple Choice Exam Questions if you are a teacher.
- Evolve more efficiently towards your ultimate goal because you will be more in control of the Random Evolutionary Process (only kidding on this third one…)
Continue reading The Three Necessary and Sufficient Conditions of Natural Selection
Mendel was born on July 20th, 1822. He is famous for his discovery of peas and genetics.
Here is his stuff translated into English.
In an BBC article describing a Royal Society paper on the rate of mutation in warm vs. cooler climates, the BBC made this statement:
DNA can mutate and change imperceptibly every time a cell divides and makes a copy of itself.
But when one of these mutations causes a change that is advantageous for the animal – for example, rendering it resistant to a particular disease – it is often “selected for”, or passed down to the next few generations of that same species.
Such changes, which create differences within a population but do not give rise to new species, are known as “microevolution”.
I suppose the BBC is into the Hopeful Monster theory or something.
Read it here, come back, and fight it out.
Junk DNA is like bigfoot. If a zoologist says something like “Hmmm… it would be cool to find bigfoot” all the other zoologists jump on him or her, drag the poor sap into the alleyway, toss on a blanket, and beat the scientist with rubber hoses until the movement stops. Same with junk DNA. If you mention that junk DNA may have a use or a role or something …. INTO THE ALLY WITH YOU!!!
The difference is, there is no bigfoot, but there may be some interesting stuff happening in the so called junk DNA.
Part of the problem is in what we call “junk.” If it does something, it isn’t junk. So, for instance, there are genes where a string of codons code for a string of amino acids. But in order for that to happen, other parts of the DNA have to be involved … parts that are not the codons coding for the amino acids that will become part of the protein. That is obiovusly not “junk” but back a few years before these bits of DNA were understood, that was “junk.” You cans see the problem.
All of which is a long run-up to a press report from Princeton talking about a possible role for junk DNA. I’ll let the Princeton press report team speak for themselves, and then I’ll enjoy reading your comments:
To comment on this post, please visit this open thread on my old blogs. The commenting system on this blog is currently broken. Sorry for the inconvenience.
Continue reading An important role for junk DNA????
I first became acquainted with the Romanovs (as historical figures, not the actual Romanovs) reading in middle school about Russian History. Later, someone turned me on to Massie’s Nicholas and Alexandra, which is quite a well known popular historical account of the last Czar of Russia and his family. Everyone knows the story of the end. The core of Czar’s family — the Czar Nicholas, his wife Alexandra, and his children — had been arrested and all of them were transported to a remote location in the Urals. A complex series of events had begun involving Czarist and Revolutionary forces. At one point, it occurred to the local revolutionary officials who were responsible for the incarceration of the Czar and his family that their execution would be a good idea, to avoid their recapture by Czarists forces in the area, and to break the loyalty of Czarist supporters still resisting the Revolution. So, on July 17th, 1918, the Czar and his family, their doctor and a nurse were escorted to an empty room in the compound in which they were being held and shot. The details are rather ghastly, as summarized by an eye witness to the event.
Continue reading The Identification of the Two “Missing” Romanov Children Using DNA Analysis
Why is there “junk DNA”? What is Junk DNA? What is a Pseudogene? What is Gene Duplication?
Goodness, you certainly do have a lot of questions. And some of them can be answered, or at least addressed, on examination of a very interesting new paper recently published about a gene that became a useless “pseudogene” a very long time ago and has recently been revived by evolution to serve once again as an active member of the community we know of as the genome. In humans.
Continue reading A dead gene comes back to life in humans
I recently posted about the work by Pagel and colleagues regarding ancient lexicons. That work, recently revived in the press for whatever reasons such things happen, is the same project reported a while back in Nature. And, as I recall, I read that paper and promised to blog about it but did not get to it. Yet.
So here we go.
Continue reading Evolution of the Lexicon
Perhaps we are all subject to falling into the trap of what I call the Hydraulic Theory of Everything. If you eat more you will be bigger, if you eat less you will be smaller. Emotional states are the continuously varying outcome of different levels of a set of hormones, forming “happy” or “stressy” or “angry” cocktails. Your brain is a vessel into which life pours various elixirs. Too much of one thing, and there will not be enough room for something else. Even political arguments are hydraulic. The ‘balanced’ middle view between two arguments is like the mixture of contrasting primary colors on a pallet.
Continue reading Why didn’t Darwin discover Mendel’s laws?