You are not the only one who has these concerns. Some Creationists are willing to allow for a population to “change slightly or a lot” - - but when they are asked to accept that at least one of the separated sub-populations can change into something VERY different … that’s when we have some major objections.
It just so happens that another thread has one or two particularly relevant postings on this topic! One of them is reproduced below:
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The Australian Case Study: Marsupial Radiation Tracked
via Genetic Fingerprints of Ancient Viruses!
This post really should get its own thread (and it will, eventually).
“Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions” by Maria A. Nilsson, Gennady Churakov, Mirjam Sommer, Ngoc Van Tran, Anja Zemann, Jürgen Brosius, and Jürgen Schmitz
PLoS Biol. 2010 Jul; 8(7): e1000436. Published online 2010 Jul 27. PMCID: PMC2910653 PMID: 20668664
Notice in the image below, the various branches of Marsupial populations that appear to be derived from a population in South America. Since the original discovery of this one population, decades ago, genetic analysis has shown that the existing marsupials of Australia are the result of this one population “radiating outward” into various empty niches - - to be vigorously exploited by emerging marsupial specialized forms - - in safe isolation from the placental mammals that were coming to dominate the rest of the world!
[Be sure to click on the images to enlarge text to a more convenient font size!]
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A “zoom” of this image will be of particular value to us later on, because it creates a convenient grouping of some fairly disparate phenotypes:
While at the top we have “shrew-like” forms, and at the bottom we have “kanga” forms aggregated, in the middle grouping, we have the suggestion that three very distinct groupings share a close heritage:
Dasyuromorphia: the group having most of Australia’s carnivorous marsupials, including
quolls,
dunnarts,
the numbat,
the Tasmanian devil,
and the thylacine.
[In Australia, the exceptions include the marsupial moles and the omnivorous bandicoots.]
Notoryctemorphia: moles, vegetarian
Peremelamorphia: bandicoots & bilbies “the characteristic bandicoot shape: a plump, arch-backed body with a long, delicately tapering snout, very large upright ears, relatively long, thin legs, and a thin tail. Their size varies from about 140 grams up to 4 kilograms, but most species are about one kilogram, or the weight of a half-grown kitten [4 kilograms = 4 half-grown kittens].”
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This is the ideal “research scenario” to see how much genetic change occurs, and how quickly - - according to Evolutionary Theory - - to accomplish divergence into three distinctive “forms” of marsupials!
Australia provides the perfect example of how 3 different populations, surprisingly closely related via Common Descent, can come to look dramatically different from the original population!
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