Platypus thumbs its nose (or bill) at evolutionary scientists
Recent publication of the platypus genome makes evolution even more problematic
The platypus (Ornithorhynchus anatinus) is a strange animal, inside and out. On the outside, a curious amalgamation of parts from diverse animal groups makes it one of the oddest creatures on the planet. It has the fur and milk glands of a mammal; it has a duck-like bill; it nurses its underdeveloped young (like a marsupial, though not in a pouch); it lays reptile-like eggs; and the males have reptile-like poison in a hind-leg spur. But all that is well known. For curiosity’s sake, we also want to know what a platypus is on the inside. What genes does it carry? To what other animal is it most similar? Evolutionists want to know this also, for the platypus has been a thorn in their side since its discovery over 200 years ago. Because this strange creature defies easy categorization, perhaps it would be easier to discuss its evolutionary origin if they could sequence the platypus genome (its full complement of hereditary information carried on its DNA).
The platypus genome was recently published,1 but it turns out that this creature is no less strange on the inside than it is on the outside. With about 18,500 protein-coding genes, the platypus is quite normal in that regard (the human, chimp, cat, chicken, nematode, and sea anemone genomes have approximately the same number of genes). However, the platypus shares some of its genetic parts with mammals, reptiles and birds, and the ordering of these parts is not what one would necessarily expect. If the chimeric (formed from mixed parts) nature of the platypus body plan was awkward for evolutionary expectations, the chimeric nature of the platypus genome is no better.
According to secular scientists, this strange creature is one of the oldest mammals, supposedly splitting off from the line that gave rise to marsupials (kangaroos, koalas, opossums, etc.) and the eutherians (mice, monkeys, man, etc.) around 166 million years ago.2 Platypus fossils have supposedly been found as far back as 111 million years ago,3 though ancient remains indicate the animals were larger than the modern version and had teeth (see The platypus: Still more questions than answers for evolutionists).
Here is a short list of some of the chimeric features found within the platypus genome:1
- Similar poison, but supposedly evolved independently from a similar gene family
- Reptile-like microsatellite DNA
- A few large and many small chromosomes
- vitellogenin egg-yolk protein (also found in fish)
- two ZPAX genes (also found in amphibians and fish)
- X chromosome similar to avian sex chromosome Z, but another chromosome is similar to the mouse X, and still another is similar to the human X
- some bird-like microRNAs
- four genes associated with the zona pellucida (helps with egg fertilization)
- casein (milk protein) genes
- some mammal-like microRNAs
- Antibacterial proteins
Platypus-specific features (these may be general monotreme features, but not much is known about the genetics of the only other monotreme, the echidna)
- 10 sex chromosomes (5 X and 5 Y)
- 50% of the genome is repetitive (like human), but these are mostly SINEs (Short Interspersed Elements) without the Alu elements (a very abundant type of SINE found only in the great apes and humans).
- A very high GC content , with an even distribution (Guanine and cytosine form stronger bonds than adenine and thymine and thus affect DNA stability and folding. The specific dimer, CG, is a site of DNA methylation, which can be used to turn genes on and off.). Eutherians and chickens have about 41% GC and humans have characteristic GC-rich regions. The platypus has a 45.5% GC, which is extraordinarily high.
- Females do not have nipples and exude milk in discrete skin patches. This seems primitive to the evolutionist, who claims that teats did not evolve until after monotremes split off, but it is really a design consideration, for this method of feeding suits the baby platypus mouthparts perfectly.
Adam Felsenfeld, director of the Large-Scale Sequencing Program at the US National Human Genome Research Institute, exemplifies the evolutionists’ response to the platypus genome sequence: ‘I find it fascinating that genomic features of what are now two separate lineages can coexist in the genome of a single organism.’4
Here comes the crucial part of the new genomic data. In order to draw conclusions, one must assume quite a bit about the history of the animal. Being that the monotreme lineage supposedly split off from the marsupial and eutherian lines so long ago, an evolutionist might expect the monotremes to contain genetic information that has since been lost in the other two lineages. But finding such evidence does not prove the assumption behind it. A creationist, on the other hand, might expect the monotremes to be unique in and of themselves. Therefore, any new or shared features would not tell us anything about the evolutionary history of the animal. The claim that a number of genes have been ‘lost’ in the eutherians, based on the fact that they are found in platypus and non-mammalian species (birds and reptiles), is nothing more than circular reasoning—it assumes the very thing that it then claims to prove.
Photo by Dave Watts <soer.justice.tas.gov.au>
We must be very careful about using genetic similarity or dissimilarity to prove ancestry. While the human and chimpanzee genomes proved to be similar (as we might expect between two species with similar morphology, diet, and habitat, but see Another evolutionary truth now conceded to be myth), there have been some surprises in the world of genetic phylogeny (e.g. Saddle up the horse, it’s off to the bat cave). The platypus is a surprise as well. The chimeric nature of its genome creates a bizarre presence/absence table of features, some of which are shared with one group, and some of which are shared with others. It is very difficult to make a pattern of presence and absence into an evolutionary argument. Cladistics is a field that studies the hierarchical ordering of traits among diverse animals. A cladist will take a table of presence/absence data and use it to draw an evolutionary tree. But there are problems with this approach, as many cladists have found out (see Flying dinosaurs, flightless dinosaurs and other evolutionary fantasies and ‘Phylogeny and Classification (Systematics)’ under The Biotic Message: Evolution versus Message Theory). Even evolutionists need to concede that we are not in fact sampling an evolutionary tree, but the terminal branches. Indeed, there is little to no evidence that any of the evolutionary nodes (missing links) ever existed. Try as we might, we cannot get into the fossil record to study the genetics of the nodes.
Summary and conclusion
The platypus genome is just another example of a species containing a mixed (or ‘mosaic’) assortment of parts. Despite the evolutionary hype associated with its sequencing, the platypus genome most assuredly does not support the idea that it shares a common ancestor with the rest of the mammals, birds, and reptiles.
- Genome consortium, Genome analysis of the platypus reveals unique signatures of evolution, Nature 453:175-183, 2008. Return to text.
- Bininda-Emonds, O.R.P., Cardillo, M., Jones, K.E., MacPhee, R.D.E., Beck, R.M.D., Grenyer, R., Price, S.A., Vos, R.A., Gittleman, J.L. and Purvis, A., The delayed rise of present-day mammals, Nature 446:507-512, 2007. Return to text.
- Rowe, T., Rich, T.H., Vickers-Rich, P., Springer, M., and Woodburne, M.O., The oldest platypus and its bearing on divergence timing of the platypus and echidna clades, Proceedings of the National Academy of Sciences USA 105(4):1238-1242, 2008. Return to text.
- Brown, S., Top billing for platypus at end of evolution tree, Nature 453:138-139, 2008. Return to text.