Saturday, January 23 2010: Macroevolution
This is an expansion to item #2 from my New Year's eve rant.
Many theists are fond of saying "yeah, but that's microevolution. that's just adaptation. there's no evidence for macroevolution - of one species turning into another."
Oh really? Well, in fact, there is. It's called the fossil record. Evolutionary sequences for hominids, whales, and horses are three that I, a lowly non-professional science fan, can think of off the top of my head. The fossil evidence clearly shows changes over time with one species transitioning into another. There is also the world famous Galapagos finches.
However, implicit in the statement that there's no macroevolution is the assumption that there is some sort of genetic wall between species which allows them to vary within certain defined boundaries but not to evolve and thereby cross those boundaries. Not only is there positive evidence of evolutionary sequences that show transitional species, but what we are now discovering as we sequence genomes and unravel the puzzles of molecular biology is a complete lack of evidence for this suggested inter-species wall.
1. Metabolism - there are 3 or 4 metabolic pathways which are shared by all of life (glycolysis, anaerobic respiration (fermentation), the Krebs cycle). Archaeans, bacteria, trees, mushrooms, and humans all break down glucose the same way. There's not even a wall separating the disparate domains of life, let alone species within those domains.
2. Cytochrome C - this protein is used widely by animals and plants and the amino acid sequences for widely disparate species are remarkably similar. Humans and chimps have the same amino acid sequence for cytochrome c and their sequence differs with that of rhesus monkeys by only one amino acid.
Many theists are fond of saying "yeah, but that's microevolution. that's just adaptation. there's no evidence for macroevolution - of one species turning into another."
Oh really? Well, in fact, there is. It's called the fossil record. Evolutionary sequences for hominids, whales, and horses are three that I, a lowly non-professional science fan, can think of off the top of my head. The fossil evidence clearly shows changes over time with one species transitioning into another. There is also the world famous Galapagos finches.
However, implicit in the statement that there's no macroevolution is the assumption that there is some sort of genetic wall between species which allows them to vary within certain defined boundaries but not to evolve and thereby cross those boundaries. Not only is there positive evidence of evolutionary sequences that show transitional species, but what we are now discovering as we sequence genomes and unravel the puzzles of molecular biology is a complete lack of evidence for this suggested inter-species wall.
1. Metabolism - there are 3 or 4 metabolic pathways which are shared by all of life (glycolysis, anaerobic respiration (fermentation), the Krebs cycle). Archaeans, bacteria, trees, mushrooms, and humans all break down glucose the same way. There's not even a wall separating the disparate domains of life, let alone species within those domains.
2. Cytochrome C - this protein is used widely by animals and plants and the amino acid sequences for widely disparate species are remarkably similar. Humans and chimps have the same amino acid sequence for cytochrome c and their sequence differs with that of rhesus monkeys by only one amino acid.
beowulf wrote: