Did Mitochondria Originate from Bacteria?
Did Mitochondria Originate from Bacteria?
A popular theory among evolutionary biologists for the origin of
mitochondria is that they were once free-living organisms that became
incorporated into cells. However, from what we know of genetics, any
free-living organism would probably need at least 256 genes and at
least about 300,000 base pairs of DNA. All free-living organisms
today have significantly more DNA than this. Mitochondria have only
about 16,000 base pairs of DNA. (Brian Speer informs me that mammal
mitochondrial DNA appears to have about 16,000 - 18,000 base pairs and
animals in general have from 14,000 to 39,000 base pairs of
mitochondrial DNA. Flowering plants have from 208,000 to 2,400,000
base pairs. See N.W. Gillham's "Organelle Genes and Genomes" p.51.)
So mammal mitochondria would have had to lose a lot of DNA in the
process of becoming incorporated into cells! It seems strange that
this would happen, when about 97 percent of the DNA of mammals is
supposed to be non-functional, and yet they have not been able to get
rid of it in over 60 million years of evolution, according to the time
scales generally accepted by scientists.
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