The 1999 comedy Dogma
opens with a disclaimer, exhorting the audience to remember that “even
God has a sense of humor. Just look at the Platypus. Thank you and
enjoy the show. P.S. We sincerely apologize to all Platypus enthusiasts
out there who are offended by that thoughtless comment about Platypi.
We at View Askew respect the noble Platypus, and it is not our
intention to slight these stupid creatures in any way. Thank you again
and enjoy the show.”
God expressed his sense of humor, of course, in assembling a
creature that is a little bit mammal (the platypus, a native of
Australia, produces milk and is furry), a little bit reptile (it lays
eggs and has venom, released from spurs in the hind legs) and a little
bit bird (eggs again, plus it has a bill like a duck as well as webbed
feet). Its cognitive capacity and/or nobility we’ll leave to the guys
at Dogma, but one particular platypus—Glennie, from New South
Wales, Australia—has made scientists smarter: an international team of
researchers from the U.S., Australia, England, Germany, Israel, Japan,
New Zealand and Spain collected her DNA and from it sequenced the platypus genome, they’re announcing today in papers in Nature and Genome Research.
The platypus genome consists of roughly 2.2 billion pairs of
chemical “letters,” those As, Ts, Cs and Gs that spell out a species’
genetic code. (Humans have about 3 billion.) Within those letters are
some 18,500 genes, compared to maybe 24,000 in humans.
Not surprisingly, the platypus genome is an amalgam of mammal, reptile and bird DNA, too.
Like reptiles, the platypus (Ornithorhynchus anatinus)
has genes for egg laying. Its venom comes from genes that are
duplicates of genes that evolved in ancestral reptiles, which is also
the source of venom in today’s reptiles. Like mammals, it has genes for
lactation (though, lacking nipples, it nurses its young through the
abdominal skin). Like birds, it has a weird way of determining sex: of
its 52 chromosomes, 10 are sex chromosomes (in humans, the X and Y, of
23 chromosomes, are sex chromosomes), and the platypus X resembles the
sex chromosome of birds, called Z. A female platypus has five pairs of
X chromosomes, while males have five Xs and five Ys. The platypus
genome contains both reptilian and mammalian genes involved in the
fertilization of eggs. Unlike most mammals, which have a pretty good
sense of smell, the platypus doesn’t—and its genome has about half as
many odor receptors as the mouse and other mammals.
Just one request, please. In the PR avalanche preceding this
announcement, one talked about the medical benefits that would surely
come from this feat. ("What does this discovery mean for the public?
The very real potential for advances in human disease prevention and a
better understanding of mammalian evolution.") Aren't we beyond that
yet? There have been virtually no medical benefits from sequencing the human
genome (yet), for goodness sake; can't we, just occasionally, celebrate
a feat of pure science without raising hopes that it will, you know,
cure cancer or something? Sometimes a platypus genome is just a
platypus genome.