|Baker's Yeast (Saccharomyces cerevisiae)|
Here is something for 'Intelligent Design' propagandists to cope with (probably by ignoring it, lying about it or abusing the scientists and people who report it).
Evolutionary biologists will tell us that the presence of the same or very similar genes in widely different organisms points to a common origin. Indeed, the fact that all living things can be arranged into a hierarchy of genetic similarity, and the fact that such an arrangement always has a single point at its origin, is one of the key pieces of evidence supporting descent with modification from a common ancestor.
For example, baker's yeast cells and human cells have about 450 genes in common even though they are separated by about a billion years of evolution. Although these genes differ in detail between the two species, they encode for the same things which are essential for the normal functioning of the cell.
But, 'Intelligent Design' advocates could always explain this away as the 'Intelligent Designer' using the same design in different organisms, and they can simply wave aside the fact that these genes are actually not the same design but themselves vary, and vary in a way which is also consistent with descent with modification from a common ancestor, by claiming that this is what makes different organisms different. The same gene doing the same thing as a homologue in a different organism is because they are different organisms, so their genes must be different.
Now, along comes a team from the University of Texas at Austin, Texas, USA, and throws this argument into total disarray by the simple technique of conducting experiments and producing evidence - which is why creationists and Intelligent Design propagandists never do any such thing and throw lots of mud at the scientific method hoping some will stick.
To determine whether genes retain ancestral functions over a billion years of evolution and to identify principles of deep evolutionary divergence, we replaced 414 essential yeast genes with their human orthologs, assaying for complementation of lethal growth defects upon loss of the yeast genes. Nearly half (47%) of the yeast genes could be successfully humanized. Sequence similarity and expression only partly predicted replaceability. Instead, replaceability depended strongly on gene modules: Genes in the same process tended to be similarly replaceable (e.g., sterol biosynthesis) or not (e.g., DNA replication initiation). Simulations confirmed that selection for specific function can maintain replaceability despite extensive sequence divergence. Critical ancestral functions of many essential genes are thus retained in a pathway-specific manner, resilient to drift in sequences, splicing, and protein interfaces.
What this team has done is to show that, for the same metabolic pathway or biological process, you can take homologous human genes and put them into yeast cells, and the yeast cells will continue to work perfectly well. They believe there may well be another 1000 or so genes that this can be done with.
So, any argument that differences between gene homologues in different organisms is because the 'Intelligent Designer' did it that way to make the organisms different, has been comprehensively refuted by showing that this isn't what makes species different. There is no design reason why these genes should be different at all. In fact, difference is incomprehensible as the work of an intelligence because it is utterly pointless. Any half-decent intelligence would use the same tried and tested design and not change it randomly and without purpose or benefit.
As the result of random, unintelligent genetic change, and genetic drift, it is perfectly understandable and entirely consistent with an evolutionary view of biodiversity and entirely consistent with the hierarchy of genetic difference all pointing to a single common origin as very strong evidence of descent with modification from a single common ancestor.
And once again science fails to find any evidence for Intelligent Design for the simple reason that it isn't true. It's a fraud invented for extremist political motives.
'via Blog this'