This Week in Evolution

“Where was you hid to see all that?” he cried. “It seems to me that you knows a great deal more than you should.” – The Complete Sherlock Holmes

“Our DNA is a coded description of the worlds in which our ancestors survived. And isn’t it an arresting thought? We are digital archives of the African Pliocene, even of Devonian seas; walking repositories of wisdom out of the old days. You could spend a lifetime reading in this ancient library and die unsated by the wonder of it.” -- Richard Dawkins, Unweaving the Rainbow

Like many of the characters baffled by Sherlock Holmes, I am repeatedly amazed by the detailed inferences my fellow scientists are able to draw about events in the distant past. This week’s paper:
Palaeotemperature trend for Precambrian life inferred from resurrected proteins
is a good example. Eric Gaucher and colleagues at the University of Florida and DNA2.0 Inc. used protein sequences from a variety of modern bacteria species to infer the protein sequences of their distant and more recent ancestors…

Continue reading "Ancient temperatures inferred from DNA" »

Posted by R. Ford Denison at 12:48 AM | Permalink | Comments (0)

Summary: A 39-year record of host-parasite interaction, recovered from sediment layers in a pond, is consistent with rapid coevolution.
Link: Host-parasite /`Red Queen/' dynamics archived in pond sediment

As I've discussed previously, archival samples often prove useful for answering questions that weren't being asked when the samples were collected. But what if nobody collected and preserved the samples you need for your research? Maybe you can find a "natural archive" that has what you need.

Continue reading "The ghost of infections past, present, and future" »

Posted by R. Ford Denison at 10:51 PM | Permalink | Comments (2)

This week's paper is "HIV-1 proviral DNA excision using an evolved recombinase" by Indrani Sarkar and others, published in Science (vol.316, p.1912). This paper is yet another example showing that selection (natural or artificial) can outperform design.

To illustrate the point, let me start with a well-known example from plant breeding. Suppose you wanted to make broccoli, starting with its ancestor, wild kale? You could cross them, identify which genetic differences are most responsible for the large edible inflorescence, and transfer those genes to the wild kale. But what if broccoli didn't exist?

Continue reading "Selection beats design, again" »

Posted by R. Ford Denison at 04:05 PM | Permalink | Comments (5)

This week's paper is "Palaeogenetic evidence supports a dual model of Neolithic spreading into Europe" by M.L. Sampietro and others, published online in Proceedings of the Royal Society. The paper is interesting both for its findings and for its methods.

We know that agriculture spread from the Near East -- do people in Asia call this the Near West? -- to western Europe, starting around 10,000 years ago. But did this mostly involve farmers moving, or the spread of agriculture without major movement of people?

People have tried to figure out past population movements using genetic differences among modern populations, but it would help to have genetic information from people who lived thousands of years ago, as well. This is technically challenging, however...

Continue reading "Tracing the spread of agriculture with stone-age human DNA" »

Posted by R. Ford Denison at 04:51 PM | Permalink | Comments (0)

What did our early ancestors and related species eat? Different data seemed to give different answers. This week’s paper may have helped to solve this mystery.

Isotope data suggest that tropical grasses were a big part of the diet of the hominins Australopithecus africanus and Paranthropus robustus. These grasses have CO2-concentrating C4 photosynthesis. As a result, they have a little more of the rare carbon-13 isotope, and a little less C12, relative to most other plants. So do the fossil teeth of these early human relatives, as if they ate these grasses. But the shape of their teeth, and wear patterns, are wrong if they mostly ate grass leaves or animals that ate grass. What about roots, or underground storage organs? These are an important food for some human foragers today, especially in dry climates. If our early relatives mostly ate these “USOs”, then the isotope ratios in their teeth should be like those of other species with a similar diet. Mole rats, for example.

Continue reading "Roots" »

Posted by R. Ford Denison at 05:48 PM | Permalink | Comments (0)