I Accept the Theory of Evolution
All apes except humans have 24 pairs of chromosomes. We humans are the only apes to have 23 pairs.
Evolution made a testable prediction; That somewhere in the human genome we should find evidence of chromosomal fusion. In other words, we should be able to find a fused human chromosome with the remnants of extra telomeres and centromeres.
Since the loss of all the genes in a chromosome would have been fatal to any species, scientists reasoned that if the Theory of Evolution was correct about common ancestry, one of two things must have occurred. Either two chromosomes had fused in humans’ evolutionary past, or chromosomes had split in the other apes. Using 'Occam's Razor’, which states that among competing hypotheses, the simplest explanation is most likely the correct one, the most likely event was chromosome fusion in humans’ ancestors.
Normal chromosomes have a centromere (a chromosomal locus that ensures delivery of one copy of each chromosome to each daughter at cell division.) and ends that are capped with telomeres… think of them as the aglets on shoelaces). It was postulated that if two chromosomes had fused, evidence for such an event would be found in a chromosome with two centromeres and telomeres where they did not belong. That is exactly what was found in human chromosome 2 (chromosomes are numbered by length).
It was subsequently established that the equivalent chimpanzee chromosomes contain the same genes as human chromosome 2 and if placed end to end the positions of those genes match those of the human chromosome. The same chromosomes in all other ape species also line up in the same way…. the fusion event has been confirmed.
Recently we have obtained largely complete genomes of two other human species, those of Neanderthal and Denisovans. We see the same chromosome fusion in their genomes as well, which tells us that the fusion event took place in a common ancestor.
The greatest test of any scientific Theory is in its usefulness as a predictive tool. In this case, as in many others, the Theory of Evolution has delivered.
Evolution made a testable prediction; That somewhere in the human genome we should find evidence of chromosomal fusion. In other words, we should be able to find a fused human chromosome with the remnants of extra telomeres and centromeres.
Since the loss of all the genes in a chromosome would have been fatal to any species, scientists reasoned that if the Theory of Evolution was correct about common ancestry, one of two things must have occurred. Either two chromosomes had fused in humans’ evolutionary past, or chromosomes had split in the other apes. Using 'Occam's Razor’, which states that among competing hypotheses, the simplest explanation is most likely the correct one, the most likely event was chromosome fusion in humans’ ancestors.
Normal chromosomes have a centromere (a chromosomal locus that ensures delivery of one copy of each chromosome to each daughter at cell division.) and ends that are capped with telomeres… think of them as the aglets on shoelaces). It was postulated that if two chromosomes had fused, evidence for such an event would be found in a chromosome with two centromeres and telomeres where they did not belong. That is exactly what was found in human chromosome 2 (chromosomes are numbered by length).
It was subsequently established that the equivalent chimpanzee chromosomes contain the same genes as human chromosome 2 and if placed end to end the positions of those genes match those of the human chromosome. The same chromosomes in all other ape species also line up in the same way…. the fusion event has been confirmed.
Recently we have obtained largely complete genomes of two other human species, those of Neanderthal and Denisovans. We see the same chromosome fusion in their genomes as well, which tells us that the fusion event took place in a common ancestor.
The greatest test of any scientific Theory is in its usefulness as a predictive tool. In this case, as in many others, the Theory of Evolution has delivered.
56-60, F
