Top 10 Missing Links
Discoveries that have helped build the puzzle of mankind's evolution.
Vestigal Organs
Darwin argued that useless limbs and leftover organs are evidence of evolution.
The findings suggest that about 9 percent of the human genes examined are undergoing rapid evolution.
"Our study suggests that natural selection has played an important role in patterning the human genome, " said Carlos Bustamante, a biologist at Cornell University.
A separate study announced last month indicated the human brain is still evolving, too.
Compared to chimps ...
Bustamante's team found that the genes most affected were those involved in immunity, sperm and egg production and sensory perception. A comparison between human and chimpanzee genomes found that these genes have undergone more changes in humans than in chimps, despite the fact that the two species shared a common ancestor some 5 million years ago.
The genes for a group of proteins important for switching other genes on and off, known as "transcription factors, " were found to vary significantly in humans and chimps. One reason for this could be that turning a gene on or off is easier than changing the gene itself.
"We believe that if you want to evolve a system, it's usually easier to tweak when the protein gets turns on or the total amount of a protein as opposed to the amino acid itself, " Bustamante said.
Negative selection
The validity of Darwin's natural selection has been attacked lately by a small but vocal group who argue that it cannot explain all the complexity seen in nature. They advocate a concept called "intelligent design, " in which a higher being is responsible for the variety of life. Scientists dismiss intelligent design as cloaked creationism and say that there are no significant problems with the widely accepted theory of evolution.
While mainstream scientists do not need further evidence that natural selection occurs, Bustamante's work provides examples of its pace and extent and offers the promise of medical advances down the road.
Another 13 percent of the genes examined in the study showed evidence for negative selection, whereby harmful mutations are weeded out of the population. These included some genes implicated in hereditary diseases, such as muscular dystrophy and Usher syndrome. The latter is the most common cause of congenital blindness and deafness in developed countries.
Medical geneticists are interested in finding genes sensitive to negative selection because they might one day be useful for predicting an individual's likelihood of developing a disease if the types of mutation to a gene and the environmental conditions are known.
Being able to determine which classes of genes are particularly vulnerable to negative selections is a first step, Bustamante said.
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using scientific methods. The term "natural science" is used to distinguish the subject matter from the social sciences, which apply the scientific method...
The Darwin–Wedgwood family is actually two interrelated English families, descended from the prominent 18th century doctor, Erasmus Darwin, and Josiah Wedgwood, founder of the pottery firm, Josiah Wedgwood and Sons, the most notable member of which was Charles...
Artificial selection (or selective breeding) describes intentional breeding for certain traits, or combination of traits. The term was utilized by Charles Darwin in contrast to natural selection, in which the differential reproduction of organisms with certain...
