Ardipithecus ramidus; four feet to two

In the evolution of humans, there was a point in time when our ancestors did not walk on two feet, but instead moved around on four. As the ancestors of humans evolved, they eventually reached a point where the transition to two feet began to occur. For a time, the fossils found detailing such a transition were of Australopithecus, a bipedal creature which seemed to sprout up in our evolutionary history 3.7 million years ago (1).  Australopithecus had multiple novel adaptations associated with bipedalism, causing many scientists to believe Australopithecus to be the result of a sudden evolution of bipedalism in the ancestors of humans. At the same time, other scientists believe that bipedalism was unlikely to have suddenly shown up in Australopithecus with fully formed adaptations. Instead, they believed it was the result of a more gradual process, with multiple distinct ancestors in-between. Unfortunately for scientists who believed the gradual step process, there were no fossils to support such a hypothesis until the discovery of a new species known as Ardipithecus ramidus, in November 1994, whose skeletons were discovered in Ethiopia(2). Continue reading “Ardipithecus ramidus; four feet to two”

Jumping Genes and the Evolution of Pregnancy

The human genome is made up of over three billion base pairs, the building blocks of DNA, but only a small part of that is actually protein coding DNA. Transposable elements (TEs) are a type of non-coding DNA that makes up approximately half of the human genome, and since their discovery in the 1940s, they have carried a bad reputation. Often referred to as junk DNA or parasitic genes, TEs are a type of mobile genetic element capable of moving around or “jumping” within the genome. There are two main types of TEs: retrotransposons, which copy themselves and then reinsert the copies back into the genome and DNA transposons, which cut themselves out of the genome and move to a different site (Figure 1). When TEs move around, they sometimes land in the middle of a gene or even another TE, which is often detrimental to the function of that gene or TE. The function and potential benefits of TEs have not always been clear, but research has slowly started to unravel their mysteries. A group of scientists at Yale, lead by Gunter Wagner, recently found that TEs may have been responsible for the evolution of pregnancy in mammals.

Figure 1 : DNA transposon (1), and retrotransposon (2). Image from Broad Institute

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Great Tits and Climate Change: An Experiment to Transform Current Prediction Models

 

Great tit feeding on caterpillar. Credit Kateimi Flickr user.

Background:

Timing is everything for bringing new life into the natural world. Every year, species such as the great tit (Parus major), one of the many song birds found on the British Isles, rely on abundant food to be able to provide enough nutrients for their growing young. The presence of this food is the result of a large cascade—like a line of dominos—that begin with the smallest of microorganisms responding to environmental factors such as temperature and salt concentration. If the timing of one of these falling dominoes is slightly off, many organisms further down the line suffer and may be unable to find food at the most critical times of early offspring growth. Two particular organisms that share the same line of dominoes as the great tit are the pendunculate oak (Quercus robur) and the various caterpillars which feed on the oak’s leaves. [3] Continue reading “Great Tits and Climate Change: An Experiment to Transform Current Prediction Models”