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The Duck-Billed Platypus Gets Even More Confusing

by  Brad Harrub, Ph.D.

The duck-billed platypus has always been a thorn in the side of evolutionists (see “The Flat-Footed, Beaver-Tailed, Duck-Billed Platypus” by Nathaniel Nelson). Many evolutionists would like to simply prune it off the evolutionary tree of life, having been forced to place it on a lone branch all to itself. But the thorn has just gotten much larger, and much harder to ignore. Aside from the fact that this mammal lays eggs and possesses features found only among birds and reptiles, researchers have now discovered that the platypus boasts not two sex chromosomes like most animals, but ten (see Grützner, et al., 2004)! Roxanne Khamsi, Nature staff writer, noted:


Everyone knows that the duck-billed platypus is pretty strange. But it seems this mammal’s eccentricities extend beyond its famous bill, and habit of laying eggs, to the way its genes determine sex. Not content with one pair of sex chromosomes, the platypus (Ornithorhynchus anatinus) has five. This is the largest number found in mammals so far… (2004).

Before you write this off as simply a “non-issue” anomaly, consider for just a moment the implications. Normally, one sex chromosome from a male species combines with one sex chromosome from a female species to make a full compliment of chromosomes. With the duck-billed platypus, this combination suddenly takes on an entirely different level of complexity. As Elizabeth Pennisi, Science staff writer, admitted:

Many organisms have two sex chromosomes. Women for example have two X chromosomes, and men have one X and one Y. But in the platypus, males have five X and five Y chromosomes, while females have 10 Xs. If the male platypus’s X and Y chromosomes randomly segregated into sperm this would greatly complicate sex determination.

This latest study helps scientists understand how the duck-billed platypus is able to keep its reproduction from going amiss. In documenting this amazing feat, Grützner and his colleagues watched the ten chromosomes link up into a chain. Pennisi observed:

The chain consisted of alternating X and Y chromosomes. During the key step in sperm formation—a division that results in two cells, each with half the number of the original number of chromosomes—the X and Y chromosomes peeled off from the chain one by one and headed into separate cells, all segregating faithfully with their own kind. This ensures that half of the sperm each have five X chromosomes; the other half have five Y chromosomes (2004).

Was it by accident that these chromosomes formed this chain in alternating order, and then precisely peeled off into separate X and Y groups? This extreme complexity veritably screams “design”! Yet researchers are hastily painting an evolutionary picture to try to explain this peculiarity.

Evolutionists, however, face a daunting task. First they must explain the sudden appearance of (and reason for) double homologous sex chromosomes. How is it that at one point in time, “nature” was able to evolve a female member of a species that produces eggs and is internally equipped to nourish a growing embryo, while at the same time evolving a male member that produces motile sperm cells? And, further, how is it that these gametes (eggs and sperm) “conveniently” evolved so that they each contain half the normal chromosome number of standard somatic (body) cells? And why is this the case? Of the 46 human chromosomes, 44 are members of identical pairs, but two, the X and Y (generally referred to as the “sex chromosomes”), stand apart. Evolutionists thus are faced with the unenviable challenge of explaining not only the origin of sex chromosomes themselves, but also the evolution of two totally different sex chromosomes (X and Y). [For more on the origin of sexual reproduction and gender, the reader is encouraged to read “The Origin of Gender and Sexual Reproduction.”]

Once evolutionists overcome that gargantuan hurdle, they then must answer why this creature possesses ten chromosomes, and how it evolved the ability to recombine them. Some of the researchers point out that maybe this is a link between birds and mammals. Commenting on their findings, Grützner and his coworkers lamented: “This suggests an evolutionary link between mammal and bird-sex chromosome systems, which were previously thought to have evolved independently” (2004, p. 1). Interestingly, Darwinians place mammals on the planet 100 million years before birds. Grützner’s suggestion requires evolutionists to explain how a mammal—the duck-billed platypus—evolved its sexual reproduction from birds—a change in the evolutionary tree that would require chainsaws, massive splicing, rolls and rolls of duct-tape, and a good dose of Miracle Grow®. Most evolutionary biologists are unwilling to even “go there.” (And of course the obvious question then becomes why did this process not evolve in other mammals?)

Commenting on the new discovery, Steve Rozen, of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, remarked: “Mammals are pretty boring when it comes to sex chromosomes. The platypus is a huge exception.” Khamsi asks the obvious question: “What is the advantage of having so many sex chromosomes?” To which Rozen replied: “It’s hard to speculate on how that could have evolved” (see Khamsi, 2004). Hard to speculate indeed! What could this creature possibly gain by “evolving” such a complex and costly reproductive method? Sexual reproduction in animals with two sex chromosomes has a “selective disadvantage” of at least 50%—a disadvantage that will not budge! The duck-billed platypus has ten sex chromosomes, each of which would lose 50% of their genetic material.

Evolution cannot explain the origin of two sex chromosomes—much less ten! What is the “purpose” of so many chromosomes? And how can evolution via natural selection explain it? Would “Nature” (notice the capital “N”) “select for” sexual reproduction? As it turns out, the common “survival of the fittest” mentality cannot begin to explain the high cost of first, evolving, and then maintaining, the sexual apparatus. Sexual reproduction requires organisms to first produce, and then maintain, gametes (reproductive cells—i.e., sperm and eggs). Yet the duck-billed platypus has five times the number of sex chromosomes, and still is able to link them in a chain and then faithfully segregate them in order to maintain the correct number! Surely, to an open and honest mind, this beautiful complexity points to a Great Designer.


Grützner, Frank, Willem Rens, et al., (2004), “In the Platypus a Meiotic Chain of Ten Sex Chromosomes Shares Genes With the Bird Z and Mammal X Chromosomes,” Nature, [On-line], URL:

Khamsi, Roxanne (2004), “Duck-Billed Platypus Boasts Ten Sex Chromosomes,” Nature, [Online], URL:

Pennisi, Elizabeth (2004), “Platypus X-Files,” Science, [On-line], URL:, October 26.

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