A History of Ideas In Evolutionary Theory

Milestones in the history of evolutionary thought highlight the contributions of key Harvard figures including Asa Gray, Ernst Mayr, Stephen Jay Gould, Richard Lewontin and E. O. Wilson. This video appears in the HMNH exhibition Evolution

If you’re staying in on a Friday as I am, here’s a neat video with Niles Eldredge (who as you know co-founded the theory of Punctuated Equilibrium with SJG) discussing the origins of Punctuated Equilibrium, giving SJG annecdotes, and why he prefers for the word “equilibria” instead of “equilibrium”.

Winner of the BioArt!        
Cartilaginous fishes such as sharks, skates, and rays are the most primitive jawed vertebrates and are important species for the study of evolutionary developmental biology.  This image depicts an embryonic Little Skate, Leucoraja erinacea, sitting atop its yolk sac. The external gills appear as red strands extending from the underside of the embryo. This skate embryo is part of a research project investigating sexually dimorphic fin development and the origin of internal fertilization. This picture was taken by a  Katherine O’Shaughnessy, a graduate student working in the Cohn Lab at the University of Florida.

Winner of the BioArt!
Cartilaginous fishes such as sharks, skates, and rays are the most primitive jawed vertebrates and are important species for the study of evolutionary developmental biology. This image depicts an embryonic Little Skate, Leucoraja erinacea, sitting atop its yolk sac. The external gills appear as red strands extending from the underside of the embryo. This skate embryo is part of a research project investigating sexually dimorphic fin development and the origin of internal fertilization. This picture was taken by a Katherine O’Shaughnessy, a graduate student working in the Cohn Lab at the University of Florida.

Hey everyone! Forgive me for not posting more regularly but this semesters has just been super duper busy! Anyways, Here’s a cool video of a tour of E.O Wilson’s desk at the Harvard Museum of Comparative Zoology! Wooo! This guy has the one of the largest ant collections and some interesting ideas (some of which I don’t agree on) but anyways, Enjoy! 

Loss of external genitalia in bird evolution

External genital anatomy evolves rapidly and is remarkably diverse among animals that reproduce by internal fertilization. One of the most intriguing evolutionary transitions is the reduction and loss of the penis in most birds, despite their dependence on internal fertilization. A new study by evolutionary developmental biologists at the University of Florida reports that embryos of bird species with reduced genitalia have increased activity of genes that control programmed cell death (apoptosis) in the developing phallus. This leads to a wave of cell death that arrests outgrowth and causes regression of the phallus at embryonic stages. These findings identify a potential mechanism for reduction of the phallus during bird evolution.

On an expedition to Greenland in 1987, this University of Cambridge paleontologist unearthed remains of a creature from the Devonian Period (408-360 million years ago) that walked around swamps on four legs. Through careful study of the anatomy, Clack determined that this creature, known as Acanthostega, nevertheless didn’t have a leg to stand on—that is, these rudimentary limbs could not support the animal’s weight. Jenny Clack, Professor of Vertebrate Palaeontology at Cambridge University, recounts how she overcame setbacks before she found and described a fossil which offered new evidence of how fish made the transition onto land.

AH! I’m short of words….This is just too…. great. 

In 1905, E. G. Conklin published a remarkable fate map of the ascidian embryo. He showed that “all the principle organs of the larva in their definitive positions and proportions are here marked out in the 2-cell stage by distinct kinds of protoplasm.” This study of cell lineage has been the basis for all subsequent research on the autonomous specification of tunicates. The color plates of this study are considered to be some of the best examples of embryological illustration and descriptive anatomy.

The Logic of Science

Stephen C. Stearns outlines the importance of being a good writer in science (something I constantly try to improve on), the functionality and ontology of science, and how it is that we know what is that we know. Some of us are starting our early careers as scientists, or perhaps already are scientists, or just interested in the underlying strucuture of science. In any way, sometimes it’s nice to see/hear something encouraging that reminds us why we got became interested in science in the first place, and I think this video fulfills it’s niche well. I highly recommend it. 

Scientist shows that Psittacosaurus first walks on four legs, however as it matures it becomes habitually bipedal. 
With special permission from the Beijing Institute, Zhao sectioned two arm and two leg bones from 16 individual dinosaurs, ranging in age from less than one year to 10 years old, or fully-grown. He did the intricate sectioning work in a special palaeohistology laboratory in Bonn, Germany,
The one-year-olds had long arms and short legs, and scuttled about on all fours soon after hatching. The bone sections showed that the arm bones were growing fastest when the animals were ages one to three years. Then, from four to six years, arm growth slowed down, and the leg bones showed a massive growth spurt, meaning they ended up twice as long as the arms, necessary for an animal that stood up on its hind legs as an adult.

Scientist shows that Psittacosaurus first walks on four legs, however as it matures it becomes habitually bipedal. 

With special permission from the Beijing Institute, Zhao sectioned two arm and two leg bones from 16 individual dinosaurs, ranging in age from less than one year to 10 years old, or fully-grown. He did the intricate sectioning work in a special palaeohistology laboratory in Bonn, Germany,

The one-year-olds had long arms and short legs, and scuttled about on all fours soon after hatching. The bone sections showed that the arm bones were growing fastest when the animals were ages one to three years. Then, from four to six years, arm growth slowed down, and the leg bones showed a massive growth spurt, meaning they ended up twice as long as the arms, necessary for an animal that stood up on its hind legs as an adult.