All one species – how climate affects physical characteristics Over long periods of time, the environment will act on the genes to develop particular characteristics within a population.
THE STORY OF THE HUMAN BODY THE SEVEN MAJOR TRANSITIONS OF HUMAN EVOLUTION SKIN
Physical characteristics such as skin and eye colour, hair type and colour and body shape are determined by genetics, but can also be influenced by the environment. This gene helps determine lip shape via body fat distribution and may have been useful to Denisovans in the cold climates of their Central Asian homelands. An international team, led from CL, Aix-Marseille University and the Open University, found the the gene TBX15 was linked with genes found in ancient Denisovans, providing a clue to the origin of the gene in our species. It also appears that some physical features have been inherited from interbreeding with other ancient human species. Areas of the human genome still seem to be undergoing selection for things such as disease and skin colour. In fact, the rate of change of DNA, and thus the rate of evolution, has accelerated in the last 40,000 years. Recent DNA studies (since 2007) confirm that genetic traits have changed or adapted to new environments during this time. When humans started to spread to different parts of the world about 100,000 years ago, they encountered a variety of different climatic conditions and evolved new physical adaptations more suitable to those new climates. Early members of our species lived in Africa and had evolved physical characteristics that were similar to each other in order to survive in that climate. Humans today show an enormous diversity in appearance, however this diversity was not apparent in early Homo sapiens. Developing physical diversity: All one species but looking different This is partly related to the introduction of fluoride, which thickens dental enamel, so making teeth a little larger. However, there has been a very slight reversal in this trend in the last century as teeth have increased in size.
However, over the last 10,000 years dietary changes and technology have played a major role.Ī decrease in size has occurred in the jaws and teeth of Homo sapiens over the last 30,000 years. Overall, these changes have occurred in proportion with a decrease in body size. In fact, some people today do not have enough space in their jaws to fit their 3rd molars or wisdom teeth. The trend toward smaller jaws and teeth that was seen in our ancestors has continued in our own species.
In part, this is related to a decrease in body size that also occurred during this period, however, other factors are probably also involved. Most of this decrease occurred in the last 6,000 years. This trend has seen a reversal in our own species and our brains are now the smallest they have been at any time in the past 100,000 years. There may also be a genetic link as industrial expansion and urbanisation has brought together genetically isolated people and reduced the impacts of inbreeding due to a greater mixing of populations and their genes.įor the last two million years there has been a trend toward a bigger brain that has affected many species in our family tree. In part, this increase is due to improved diet and health care. There has been an increase in height over the last few hundred years.