Posts from the ‘evolution’ Category


The genome of Monosiga brevicollis, the choanoflagellates photographed above, was recently sequenced.

Choanoflagellates,single-celled, aquatic, eukaryotic microbes are currently biological giants in unlocking the key to the evolutionary transition from unicellular to multicellular organisms, particularly in animals.

Sponges, or animals of the phylum Porifera , serve as the most primitive extant group of animals. (You can see this on this  previously posted phylogenetic tree of the history of life). Interestingly enough, aquatic sponges possess flagellated feeding structures  called choanocytes, which are nearly morphologically identical to the single-celled organisms we call choanoflagellates.

Photo Courtesy: National Science Foundation

A cool picture, that demonstrates an even cooler possibility: being able to eventually map the entire rise of modern life through genomic studies.

Bill Nye on the danger of not believing in long-term evolution.

Berkeley evolution page, with all sorts of great lessons and outlines and stuff. Check it out!

Evolution 101

When you hear the word evolution, you may think of iconic images of Darwin and the Beagle, representations of the “tree of life,” pictures of apes and the DNA double helix. But do you realize just how thoroughly the subject seeps into our everyday lives? To give a sense of this, we asked five experts in different fields to briefly describe an example. Listen in, and find out how evolution and the process of natural selection–the survival of those creatures that are best adapted to their environment–gives us dogs, makes us such good runners, and even helps us solve crimes.

Evolution in Your Life



I had some medical trouble this week that had me dreaming of upgrading my model. The photosynthetic critter is based on the sea slug Elysia chlorotica.

I just love the biology-influenced comics of Rosemary Mosco. Here’s some animal parts she wishes she had. Me too!

Another favorite, and the whole collection at Bird and Moon.

And is promptly countered by prominent science writer John Hogan, who argues that it is merely a cultural development. Both hold that we can overcome it. The difference? Hogan states that if we believe that we are meant for war, it perpetuates our going to war with the reasoning that “it’s in our nature.” Could we really become the planet’s dominant species without a temperament for killing others though? I personally tend to lean toward Wilson’s belief, and that aggressiveness was necessary for us to survive and now that we’re one top, we fight each other for various reasons. Mr. Hogan makes some good points also though, and has just released a book on it. What do you think?

The esteemed E.O. Wilson says war is inevitable for our species

A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.

Max Planck (via yournicheintheworld)

It is not the strongest or the most intelligent who will survive but those who can best manage change.

Charles Darwin (via sushi-cupcake)


How Infectious Disease May Have Shaped Human Origins
Inactivation of two genes may have allowed escape from bacterial pathogens, researchers say

Roughly 100,000 years ago, human evolution reached a mysterious bottleneck: Our ancestors had been reduced to perhaps five to ten thousand individuals living in Africa. In time, “behaviorally modern” humans would emerge from this population, expanding dramatically in both number and range, and replacing all other co-existing evolutionary cousins, such as the Neanderthals.

The cause of the bottleneck remains unsolved, with proposed answers ranging from gene mutations to cultural developments like language to climate-altering events, among them a massive volcanic eruption.

Add another possible factor: infectious disease.

In a paper published in the June 4, 2012 online Early Edition of The Proceedings of the National Academy of Sciences, an international team of researchers, led by scientists at the University of California, San Diego School of Medicine, suggest that inactivation of two specific genes related to the immune system may have conferred selected ancestors of modern humans with improved protection from some pathogenic bacterial strains, such as Escherichia coli K1 and Group B Streptococci, the leading causes of sepsis and meningitis in human fetuses, newborns and infants.  

“In a small, restricted population, a single mutation can have a big effect, a rare allele can get to high frequency,” said senior author Ajit Varki, MD, professor of medicine and cellular and molecular medicine and co-director of the Center for Academic Research and Training in Anthropogeny at UC San Diego. “We’ve found two genes that are non-functional in humans, but not in related primates, which could have been targets for bacterial pathogens particularly lethal to newborns and infants. Killing the very young can have a major impact upon reproductive fitness. Species survival can then depend upon either resisting the pathogen or on eliminating the target proteins it uses to gain the upper hand.” More here

In the above photo, Escherichia coli bacteria, like these in a false-color scanning electron micrograph by Thomas Deerinck at UC San Diego’s National Center for Microscopy and Imaging Research, cause a variety of often life-threatening conditions, particularly among the young. Varki and colleagues suggest a genetic change 100,000 or so years ago conferred improved protection from these microbes, and likely altered human evolutionary development.

Human evolution is really cool, and who wouldn’t want to know how we got to where we are? The survivors of this bottleneck event, infectious disease or otherwise, gave us our Mitochondrial Eve and Y-Chromosomal Adam. The work being done on both of these is fascinating, especially the maps!

Real talk