The evolution of internal fertilization in vertebrates, cont.

(Note: In a later entry a reader challenged this article and I replied.)

My earlier statement, in “An absolute refutation of Darwinism,” that internal fertilization among vertebrates first appears in reptiles was incorrect. There are some amphibian species that have internal fertilization, and some that even have sexual intercourse (though copulation is probably the correct word when referring to animals). This information introduces fascinating complexities into the question of the evolution of sexual intercourse by Darwinian processes, without altering my conclusion that such evolution is impossible.

Here, from an article on “Amphibian morphology and reproduction” in the Encyclopedia of Earth, which I found via Google, is an introduction to internal fertilization in amphibians:

Amphibians accomplish fertilization of their eggs in a variety of ways. External fertilization, employed by most frogs and toads, involves a male holding a female in a pose called amplexus. In amplexus, the male releases sperm over the female’s eggs as they are laid. Less risky is the method employed by many salamanders whereby the male deposits a packet of sperm called a spermatophore onto the ground. The female then pulls it into her cloaca where fertilization occurs internally. By contrast, caecilians and tailed frogs use internal fertilization just like reptiles, birds and mammals. The male deposits sperm directly into the female’s cloaca via an intromittent organ.

Caecilians are limbless, worm-like amphibians. According to Wikipedia:

The Caecilians are an order (Gymnophiona or Apoda) of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, which makes them the least explored order of amphibians, and widely unknown….

Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species with lengths up to 1.5 m resemble snakes….

Caecilians are the only order of amphibians which only use internal insemination. The male Caecilians have a penis-like organ, the phallodeum, which is inserted into the cloaca of the female for 2 to 3 hours. About 25% of the species are oviparous (egg-laying); the eggs are guarded by the female. For some species the young caecilians are already metamorphosed when they hatch; others hatch as larvae. The larvae are not fully aquatic, but spend the daytime in the soil near the water.

75% of the species are viviparous, meaning that they give birth to already developed offspring. The fetus is fed inside the female with special cells of the oviduct, which are eaten by the fetus with special scraping teeth. Some larvae, such as those of Typhlonectes, are born with enormous external gills which are shed almost immediately. The egg laying species Boulengerula taitanus feeds its young by developing a special outer layer of skin, which the young peel off with similar teeth. Ichthyophis is oviparous and is also known to show maternal care.

Here is information on the other amphibian that practices internal fertilization, the tailed frog, Ascaphus truei:


Due to their environment the male tailed frog inserts his sperm in to the female using his “tail”. When the eggs are fertilized the female lays the eggs underneath rocks to keep the eggs from being swept away from the current. When the tadpoles develop the tadpoles latch on to the rock with their mouths against the current. [it sounds as thought there is no internal development of the fertilized eggs, the fertilization simply occurs inside the female rather than in water, then the female lays the eggs….


The biggest adaptation that this frog has besides the typical frog adaptations (skin to keep in moisture, strong hind legs for jumping, etc)is its tail. The males use the tails for mating. Unlike other frogs they can not fertilize the eggs externally. Since These frogs live in fast paced waters tailed frogs use internal fertilization.

The tadpoles also have a major adaptation. They have a mouth that can stick to smooth objects. This adaption keeps the tadpoles from being swept away.

Here is more on the tailed frog:

Description. This is a small frog (5 cm total length) that lives in clear, cold mountain streams. It is light to dark brown on the back and usually has slightly granular skin. Adult males are unique among frogs in having a tail-like reproductive organ; females have very small, somewhat tubular cloacal projections.

Distribution. The tailed frog occurs in the Cascade Mountains and Coast Range from southern Canada to northern California, in the Blue Mountains of eastern Washington and Oregon, and in the Rocky Mountains of Northern Idaho and probably western Montana.

So, sexual intercourse and internal fertilization first appear in some amphibians, not in reptiles. Yet the basic challenge I posed to Darwinism remains, which is that the entire suite of complementary organs and behaviors still have to develop, as a result of chance random mutations, simultaneously in both sexes. The male still has to develop the organs, organic functions, instincts, and behaviors to deposit the sperm inside the female, and the female still has to develop the organs, organic functions, instincts, and behaviors to receive the male organ and sperm. And these two sets of mutations and their accompanying phenotypical changes must occur simultaneously in both sexes, otherwise the organisms would fail to produce offspring and their mutations would not be preserved.

However, is not this difficulty overcome via a “transitional form,” namely the salamander? As the Encyclopedia of Earth article tells us, the female salamander picks up the male sperm packet and puts it inside her cloacum and has internal fertilization. This extraordinary behavior would seem to reduce significantly the number of simultaneous random mutations that must occur in order for the male and female to mate successfully. Instead of there having to be both the simultaneous development of the complementary mating organs and behavior in both sexes and the development of the female’s internal reproductive functions, the latter would already be in place, so that only the sexual contact would have to be added to the picture in order to create the new species behavior.

Here’s a description of salamander reproduction, from an article for Cornell students on how to spot salamanders on or near the Cornell campus:

Because of the high levels breeding activity that take place when the salamanders emerge, you may encounter signs of the salamanders’ presence, besides the actual animals themselves. The species of interest here use a particular form of internal fertilization. When a male courts a female, he will drop a spermatophore on the floor of the pond (or a branch or rock or whatever he thinks is the most attractive). The spermatophore consists of a gelatinous bottom and a cap containing the spermatozoa (the genetic material that will give rise to the embryo). The female will then come along and pick up this spermatophore with her cloaca to fertilize the eggs inside her body.

The really cool part is that you can see all of this as its happening. If you go out to vernal pools and shine your flashlight into the water you might be able to see bright white specks on the floor of the pond; these are the spermatophores. If you’re really lucky, you might also be able to catch the salamanders in the act of courting females, mating, and dropping off and picking up spermatophores. Additionally, look for clear, gelatinous masses floating on the surface of the water, or attached to vegetation on the surface. These are the egg sacs the females lay after internal fertilization occurs.

Now, if we imagine an evolutionary scenario in which the way of reproduction represented by the salamander (the female picks up the male sperm packet and places it inside her cloacum, followed by internal fertilization) precedes the way of reproduction represented by the tailed frog (the male inserts his sperm directly into the female cloacum, followed by internal fertilization), fewer simultaneous innovations would be needed for the tailed frog method of reproduction to be achieved, because, as I’ve said, the system of internal fertilization would already be there, prior to the evolution of direct sexual intercourse. This means that instead of the odds against the evolution of sexual intercourse by Darwinian processes being (to pick out a number suggesting total impossibility) ten billion to one, they are, say, a billion to one. It remains the case that it is impossible for UNRELATED CHANCE RANDOM MUTATIONS TO OCCUR SIMULTANEOUSLY IN THE MALE AND FEMALE giving the male the behavior and the organs to fertilize the female internally, and giving the female the behavior and organs to receive the male.

But that’s not all. The salamander, our transitional form, instead of making Darwinian processes less unlikely, introduces its own impossibility into the situation. The male salamander had to develop, by chance random mutations, the organs, functions, and external behavior to produce the spermatophore packet (which is itself a complex object) and lay it on the bottom of the pond, and, at the same time, also by chance random mutations, the female salamander had to develop the organs and behaviors to pick up the spermatophore from the floor of the pond and deposit it inside her cloacum.

Conclusion: it’s not just highly complex organs such as the eye and the bacterium flagellum (those two overused examples) that random Darwinian variations cannot possibly create, but the whole of life.

* * *

Addendum 1: see this article on amplexus, the mating of frogs and toads by means of the male tightly clasping the female for hours or even days, prior to externally fertilizing her eggs. There is even multiple amplexus, which is spectacularly gross, and the kind of thing that convinces the more squeamish among us that God could not possibly have created the phenomena of life.

* * *

Addendum 2: The thought that gave rise to the article “An absolute refutation of Darwinism” and this follow-up article is simple. The familiar examples of irreducible complexity, the eye and the bacterium flagellum (and by the way it is unfortunate and very boring that only those two examples are used in the debate, when there are thousands), involve numerous chance random mutations that would have to occur simultaneously in one organism. By contrast, a change in the method of sexual reproduction involves numerous chance random mutations that would have to occur in a male organism and a female organism simultaneously. This seemed to me an even more dramatic and definitive demonstration of the impossibility of Darwinian evolution than the familiar examples of the eye and the flagellum.

Moreover, not only must these perfectly mutually complementary mutations occur in a male and a female member of the same species at the same time, but they must occur in the same place. Out of the entire range of habitat of the species in question, the mutated male and his perfectly complementarily mutated female counterpart have got to be living in the same neighborhood, otherwise they couldn’t meet up and launch a new way of producing offspring together. Now, I’ve heard of fate, but isn’t the belief in such a meeting of perfectly matched lovers, each one being the only one for the other in the whole world, taking things a little far—especially for the Darwinians, who insist that all the innovations in living organisms appear by accident?

Posted by Lawrence Auster at January 26, 2008 02:36 PM | Send

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