Lizards moving from eggs to live birth: evolution in action?
Published: 18 November 2010 (GMT+10)
Lizards reproduce in an amazing variety of ways. Some lay eggs (oviparity) and some bear live young (viviparity). Most species rely mostly on egg yolk for nutrition during embryonic development; a few have next to no yolk and rely completely on a placental connection to the mother. Some lizard placentas even compare with the complexity of mammalian placentas. Some species can vary the timing of birth. There are a rare few species that even have variety in their reproductive mode.
National Geographic recently reported on one of these rare few species that have differing reproductive modes between populations—one of only three in the world—the yellow-bellied three-toed skink Saiphos equalis.1,2
S. equalis is a small skink located mainly from the mountains to the coastline of New South Wales, Australia.
Smoke and mirrors
National Geographic portrayed these skinks as evolving from egg-laying to live birth:
“Evolution has been caught in the act, according to scientists who are decoding how a species of Australian lizard is abandoning egg-laying in favour of live birth.”1
This is mere smoke and mirrors; there’s no evidence S. equalis is abandoning oviparity. No oviparous populations of S. equalis are showing signs of changing reproductive mode. There is a difference in reproductive mode between populations that appears to be related to differences in climate, but individual skinks are stable; they don’t change reproductive mode throughout their lifetimes even when climates change.3
Even if some populations of S. equalis were genuinely making a transition from one reproductive mode to another, the species as a whole is not moving in that direction; only certain populations.
All your eggs in one basket?
Evolutionists believe this is a transition from oviparity to viviparity because of the way they interpret observations about lizard paleontology and biology. Oviparous organisms appear lower in the stratigraphic column than viviparous organisms, and evolutionists interpret this ‘geologic column’ as a time sequence of millions of years of evolution, so they believe oviparity came before viviparity. They believe the current variation in birthing practice in lizards is related to a general trend to move from oviparity to viviparity. As a result, evolutionists state that viviparity has evolved independently in reptiles nearly 100 times, and that squamates (lizards and snakes) account for the vast majority of such events.1,4 S. equalis becomes a prime example because both reproductive modes exist within the one species, and oviparity in S. equalis is somewhat intermediate in form between ‘normal’ lizard oviparity and viviparity.
There is however a another option: many types of lizard (including S. equalis) originally had the capacity for both reproductive modes, but due to natural selection most subsequently lost the ability for one or the other. This is consistent with the post-Flood dispersion of biblical kinds. Evolutionists don’t generally consider this possibility because it’s a process of information segmentation and loss, which gives no support to microbes-to-microbiologists evolution, and also gives no chronological priority to oviparity.
From this, we would expect to see much variation in the mode of birth/placental complexity in lizards because they originally had the information for numerous modes of reproduction. As described above, there is a multitude of reproductive methods among lizards.5
We would also expect most species to have only one reproductive mode because as the lizards spread from the ark after the Flood, genetic bottlenecks would have given rise to rapid diversification under natural selection. We find that most lizard species around the world are either oviparous or viviparous, but not both.2,6
We may, however, expect to see a few species that retain the diversity, but not many, since we would expect most to have specialized after the genetic bottleneck of the Flood. Since there are only three known species of lizard that retain diversity in reproductive mode (S. equalis,2,7 Lerista bougainvillii,8 and Lacerta vivipara9), this is also consistent with the biblical model.
Is it an intermediate form?
Viviparous populations of S. equalis retain eggs to the later stages of embryonic development, whereas most oviparous lizards lay their eggs much earlier.5 Therefore, evolutionists have a point that S. equalis is significant for understanding mechanisms of reproductive variation among lizards because it represents an intermediate form on the oviparity–viviparity spectrum of lizards. However, this does not necessarily mean that since S. equalis is an intermediate form that it is evidence for the evolution of viviparity de novo. This intermediate form can also be interpreted as a parallel of an ancestral form in (at least some) lizards that had the potential for both oviparity and viviparity. Polarization between reproductive modes occurred, as Smith and Shine pointed out, because the intermediate form is not reproductively stable long-term.5 But this favours natural selection from an ancestrally large gene pool rather than the repeated de novo creation of viviparity because specialization and information loss is the norm in biology—it is commonly observed.
The only ‘transition’ that may possibly arise is if the skink populations are on the whole ‘transitioning’ from the warmer coastal climates to the colder mountain climates. The skinks from within contiguous populations don’t show variety in birthing practice with changing climate. Natural selection likely weeded out the variety in birthing method in individual populations, though the individual populations are still not yet reproductively isolated from one another.
Natural selection involves only a sorting (often involving a loss) of genetic information, which adds nothing new. As a population becomes more specialized via natural selection, it is less capable of adapting to changing conditions in the future. The problem is that evolution requires vast amounts of new information to be constantly added to the biosphere.
Moreover, de novo creation of viviparity requires the production of new regulatory systems which could only evolve via many information-adding random mutations. However, experimental science is hard-pressed to find examples of random mutations that produce new information, where neo-Darwinism requires many.10 We also see an inexorable trend of genetic deterioration caused by near-neutral mutations that will eventually lead to the extinction of all multi-cellular life.11,12 Molecules-to-man evolution expects the exact opposite of what we see happening in biology, so the de novo creation of viviparity via evolution is highly unlikely.
Despite what evolutionists think they are seeing, they’re really just seeing one more example of natural selection, which is not microbes-to-man evolution. A biblically consistent explanation of the data is not only simpler, but fits better with what we know about natural selection and biological variation.
- Handwerk, B., Evolution in action: lizard moving from eggs to live birth, National Geographic News, 1 September 2010 (accessed 15 September 2010). Return to text.
- Stewart, J.R., Mathieson, A.N., Ecay, T.W., et al., Uterine and eggshell structure and histochemistry in a lizard with prolonged uterine egg retention (Lacertilia, Scincidae, Saiphos), J.Morphol. doi: 10.1002/jmor.10877, published online before print 16 August 2010. Return to text.
- Smith, S.A. and Shine, R., Intraspecific variation in reproductive mode within the scincid lizard Saiphos equalis, Aust. J. Zool. 45:435–445, 1997. Return to text.
- While evolutionists believe the general trend is irreversible, there is considerable debate over whether there are individual cases of reversion back to oviparity. It illustrates that the biblical alternative is a simpler approach than the extreme convergence and reversion postulated by evolutionary explanations of the reproductive diversity among lizards. Return to text.
- Blackburn, D.G., Squamate reptiles as model organisms for the evolution of viviparity, Herpetol. Monogr. 20:131–146, 2006. Return to text.
- Smith and Shine, ref.3, p. 444. Return to text.
- Smith, S.A., Austin, C.C. and Shine.R., A phylogenetic analysis of variation in reproductive mode within an Australian lizard (Saiphos equalis, Scincidae), Biol. J. Linn. Soc. 74:131–139, 2001. Return to text.
- Qualla, C.P., Shine, R., Donnellan, S. and Hutchinson, M., The evolution of viviparity within the Australian scincid lizard Lerista bougainvillii, J. Zool. 237:13–26, 1995. Return to text.
- Arrayago M.J., Bea, A. and Heulin, B., Hybridization experiment between oviparous and viviparous strains of Lacerta vivipara: A new insight into the evolution of viviparity in reptiles. Herpetologica 52:333–342, 1996. Return to text.
- Batten, D., Clarity and confusion: A review of The Edge of Evolution by Michael J. Behe, J. Creation 22(1):28–33, 2008. Return to text.
- Sanford, J., Genetic Entropy and the Mystery of the Genome, 3rd edn, FMS Publications, New York, 2008. Return to text.
- Williams, A., Mutations: evolution’s engine becomes evolution’s end! J. Creation 22(2):61–62, 2008. Return to text.
A very interesting article. This issue was first brought to my attention by an Evolutionist. Such an argument caught me off guard, but I see you have a very good answer. I have a few questions, however.
Firstly, what exactly is it that's happening? Have we observed a lizard hatching from an egg that then goes on to produce live young, or is it just a population of two skinks that reproduce in two different ways?
Secondly, with the ones you believe originally had the capacity for both, in what way do you believe they reproduced, and do you belive they laid eggs bearing lizards that reproduced with viviparity, or vice versa?
Thanks for the article.
In answer to your questions:
- This situation is the case of different populations of the same species of skink that have different reproductive modes—some populations lay eggs, and other populations give birth to live young.
- I think it’s likely that the original skinks had the ability to vary their birthing mode depending on the climate. This ability to vary was likely lost as the skink populations became geographically isolated and a stable climate (whether warmer or cooler) lead to a selection preference for one birthing mode over another in different populations. This lead to a stark polarization in birthing modes among most lizards and snakes, but a few (such as Saiphos equalis) haven’t differentiated as far as most.