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Welcome to our Epic Failures in Evolution series. I am your host Rich Deem of GodAndScience.org
Our second example of evolutionary epic failures comes from speciation of Goatsbeard plants,
which were supposed to have “evolved” since 1940.
This story comes from the TalkOrigins website. “Three species of wildflowers called goatsbeards
were introduced to the United States from Europe shortly after the turn of the century.
Within a few decades their populations expanded and began to encounter one another in the
American West. Whenever mixed populations occurred, the species interbred (hybridizing)
producing sterile hybrid offspring. Suddenly, in the late forties two new species of goatsbeard
appeared near Pullman, Washington. Although the new species were similar in appearance
to the hybrids, they produced fertile offspring. The evolutionary process had created a separate
species that could reproduce but not mate with the goatsbeard plants from which it had
evolved.” So, this is speciation in action! Evolution is confirmed!
The TalkOrigins website didn’t tell us how this “evolution” had occurred. Was it
due to some massive flurry of mutations and natural selection? Most species (including
us) are diploid – that is, we have two copies of each chromosome. Goatsbeard species have
6 pairs of chromosomes. In normal cell division, called mitosis, the paired chromosomes are
duplicated then pulled to opposite ends of the cell as it divides. The result are two
identical daughter cells that contain 6 pairs of chromosomes.
In meiosis of sex cells or gametes, there is a reductive cell division, in which the
final cell division is not accompanied by chromosomal duplication. So, each daughter
cell gets only one copy of each chromosome. The gametes are termed “haploid.”
The embryo is formed when the two haploid gametes fuse, restoring the diploid chromosome
number. In the case of two different goatsbeard species,
fusion of gametes produces a hybrid. However, since the chromosomes were not completely
compatible, the hybrid is sterile, since meiosis of the hybrid is unsuccessful.
There were two separate instances of meiosis failure in which two different species of
goatsbeard, both duplicated their chromosomes prior to the final gamete division, producing
diploid gametes. When gametes from these species combined, a tetraploid organism was produced.
You will notice that there are now 12 pairs of chromosomes instead of 6. No new information
was created when the tretraploid species was formed.
Why doesn’t the backcross work? When diploid species of Goatsbeard undergoes meiosis, there
are 6 chromosomes in the gametes. When the tetraploid species undergoes meiosis there
are 12 chromosomes. When gametes from either diploid species cross with the tetraploid
species there is a chromosome mismatch. So, the backcross fails not because of any kind
of evolution of new information, but simply because a mismatch in chromosome number.
The origination of a new species of goatsbeard was due to a single genetic event that created
a tetraploid plant. The inability of the new species to cross with parental species was
simply due to chromosomal mismatch. So, no new information was created during this “speciation”
event. The Goatbeards story is an evolutionary epic failure!
More information can be found online at our website, GodAndScience.org. Thanks for watching
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