Seeing is believing for evolutionists
But what is it that they really observe?
A supporter named Peter A., wrote asking how to answer an evolutionist’s challenge to read an article which purported to show that evolution can be observed. This person had stated, on an online forum:
“You’ve used this argument several times, that evolution is not observable. I’m not sure who told you that, but you should research it. Here’s just one very helpful link, to a list of specific examples where evolution actually can be observed (and I mean that literally, not just in that we can observe the genetic links between species, which is itself a valid point).”
The link given was to an article entitled “8 Examples of Evolution in Action”1 and included details about skink reproduction which Peter A. particularly queried.
Here is how CMI’s Philip Bell responded:
Zoologists have long recognised different modes of birth2 among otherwise related creatures:
- Oviparity (also called ovipary)—laying eggs; i.e. embryos develop outside mum’s body.
- Ovoviviparity (or ovovivipary)—embryo develops in eggs but these are retained inside mum’s body until they’re partly mature.
- Viviparity (vivipary)—the embryo matures inside mum, followed by a live birth.
I remember learning about these during my zoology degree in the 1980s. The advantages of the different forms of reproduction are well known and non-controversial. In fact, in the article link, they state:
“Skinks living on the coast tend to lay eggs, probably because the warm weather is predictable and sufficient for embryonic development. Those skinks living in the cooler mountains tend to give birth to live young, the mother’s body providing a more stable temperature. It is to be predicted that these two populations will at some point separate into different species as each population becomes fixed in its reproductive strategy.”
I have no problem with any of this. If an animal produces eggs, laying them almost as soon as they’re produced (No. 1, above) versus laying them later,3 allowing a certain amount of development (No. 2, above) is no big deal. This is part of the Creator’s variety and it makes perfect sense within a creationist worldview—speciation included. No new genetic information needs to be encoded in the genome to explain these different ‘strategies’ and a number of examples of creatures are known that can switch between these modes depending on conditions.4
However, there is a lot of difference between true placental viviparity (as in mammals and ourselves) and the types of live birth where the animal produces eggs (as in skinks) which, because particularly thin-shelled, allow some gaseous exchange and even nutrient exchange between the egg and the mum’s uterus. The ‘shell’ in such cases effectively ‘dissolves’ over time and the young are ‘born’ later. Other reptiles with true live birth (No. 3, above) are really quite different in the details.5 A problem for creationists? Not at all. They were and still are skinks—thus still the same kind of animal.
A similar-but-unrelated web article (titled “7 signs of evolution in action”) also features skinks—both items, coincidentally, are at No. 7 on the two lists. In the latter article, the claim was that “Lizard loses limbs” and my colleague Tas Walker critiqued this in May 2009. As Tas pointed out at the time:
“ … it does not take millions of years for a lizard to lose its legs. Just one mutation in one generation will do the trick. The loss of legs on lizards is consistent with, and thus points to the truth of, the biblical account of how the world came to be the way it is today … ”
We have written in more detail about limbs in lizards and snakes in the 'Related Articles' section below.
References and notes
- Article on listverse.com, accessed 14 June 2016. Return to text.
- Specialists may recognise more than the three listed below but these are the major ones. Return to text.
- Or birthing them later, after they’ve ‘hatched’ inside mum. Return to text.
- Effectively, there’s a sort of continuum, depending on the time that the eggs are retained inside the mother and the thickness of an egg’s shell. Return to text.
- Certain lizards do have viviparous forms (e.g. the skink, Saiphos equalis) but the internal reproductive anatomy and processes are distinct from that of placental mammals. Return to text.