Source: http://www.sciencedaily.com/releases/2014/12/141218210100.htm
By: Emory Health Sciences
Published: December 18, 2014 by ScienceDaily
Summary of the article
The evolution of human vision didn’t happen quickly; it required many genetic mutations in visual pigments spread over millions of years for humans to evolve from ultraviolet vision to violet vision. The speed of evolution depends on how fast the environment changes. The scabbardfish was able to change its vision very quickly because its environment changed very fast, while humans took much longer because their environment changed much slower over time. According to Shozo Yokoyama, a biologist at Emory University, we have now traced all of the evolutionary pathways, going back 90 million years, that led to human color vision.
The first step of studying the adaptive process for vision in humans was estimating and synthesizing ancestral proteins and pigments of a species. Next, experiments were conducted and carried out on them. The technique combines microbiology with theoretical computation, biophysics, quantum chemistry, and genetic engineering.
There are five different classes of “opsin” genes, which encode visual pigments for dim-light and color vision. The opsin genes change and adapt to the environment. When the environment changes, the opsin genes change too. 30 million years ago, our ancestors had evolved four classes of opsin genes, which gave them the ability to see the full-color spectrum of visible light, except for UV (ultraviolet).
After testing ancestral proteins and pigments, researchers identified 5,040 possible pathways for the amino acid changes required to bring about the genetic changes. The researchers did experiments on all 5.040 of them. 80 percent of these pathways stopped in the middle because the mutations blocked water channels that the proteins needed to function.
After conducting even more experiments and were able to identify seven essential genetic mutations that caused the loss of UV vision and developed blue sensitive pigment. Researchers discovered that the mutations had no effect individually, and only changed the pigment when they were all put together in a certain order. This certain order was the order of genetic mutations that gave humans’ ancestors colored vision rather than UV vision.
How this relates to our class:
This article relates to what we have learned in class because it describes how our ancestor evolved to change its vision to the way that humans see now. The article also mentions how natural selection played a part in making all of the ancestors have this advantageous trait after millions of years. Finally, this article talks about how evolution and natural selection relates to the environment. When natural selection occurs, it picks out traits for a species that better suit it for its environment. The faster that the environment changes, the quicker the species will have to adapt. If the environment changes more slowly, then the species will not have to adapt to it as quickly.
Based on the changes that have occurred in human vision over time, is it likely that human vision will change in the future, or has human vision "completely" evolved?
ReplyDeleteThe article that I read did not mention anything about the possible future changes of human vision. My guess is that human vision may change some, but is unlikely to change as much as it already has because humans do not usually compete with each other through natural selection based on vision.
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