Timing and causes of mid-Holocene mammoth extinction on St. Paul Island, Alaska - PNASWe probably now know what caused the final extinction of mammoths. It was a simple lack of fresh water in their last island refuge as the climate changed.
What creationists now have to tell us is why their intelligent (sic) designer decided to kill them off and why it chose this method, because it looks for all the world like the sort of thing that might well happen with a mindless, undirected natural process. But of course, a creationist has to believe nothing happens because of chance or unfortunate accident and everything happens for a purpose and according to a plan.
I'll leave them to ponder on this and see if they can come up with something better than the standard excuse when they can't think of an intelligent reason and fall back on their intelligent (sic) designer's ineffability and their limitations in being able to understand it.
What the researchers from the University of Alaska Fairbanks found was that climate change about 5600 years ago almost certainly led to what fresh water there was on St. Paul Island between Alaska and Siberia drying up to the extent that it was insufficient for the mammoth population's needs.
Significance
St. Paul Island, Alaska, is famous for its late-surviving population of woolly mammoth. The puzzle of mid-Holocene extinction is solved via multiple independent paleoenvironmental proxies that tightly constrain the timing of extinction to 5,600 ± 100 y ago and strongly point to the effects of sea-level rise and drier climates on freshwater scarcity as the primary extinction driver. Likely ecosystem effects of the mega-herbivore extinction include reduced rates of watershed erosion by elimination of crowding around water holes and a vegetation shift toward increased abundances of herbaceous taxa. Freshwater availability may be an underappreciated driver of island extinction. This study reinforces 21st-century concerns about the vulnerability of island populations, including humans, to future warming, freshwater availability, and sea level rise.
Abstract
Relict woolly mammoth (Mammuthus primigenius) populations survived on several small Beringian islands for thousands of years after mainland populations went extinct. Here we present multiproxy paleoenvironmental records to investigate the timing, causes, and consequences of mammoth disappearance from St. Paul Island, Alaska. Five independent indicators of extinction show that mammoths survived on St. Paul until 5,600 ± 100 y ago. Vegetation composition remained stable during the extinction window, and there is no evidence of human presence on the island before 1787 CE, suggesting that these factors were not extinction drivers. Instead, the extinction coincided with declining freshwater resources and drier climates between 7,850 and 5,600 y ago, as inferred from sedimentary magnetic susceptibility, oxygen isotopes, and diatom and cladoceran assemblages in a sediment core from a freshwater lake on the island, and stable nitrogen isotopes from mammoth remains. Contrary to other extinction models for the St. Paul mammoth population, this evidence indicates that this mammoth population died out because of the synergistic effects of shrinking island area and freshwater scarcity caused by rising sea levels and regional climate change. Degradation of water quality by intensified mammoth activity around the lake likely exacerbated the situation. The St. Paul mammoth demise is now one of the best-dated prehistoric extinctions, highlighting freshwater limitation as an overlooked extinction driver and underscoring the vulnerability of small island populations to environmental change, even in the absence of human influence.
Copyright © National Academy of Sciences. Open Access.
Mammoths had ranged extensively across Eurasia and North America, including the Beringia land bridge between Alaska and Siberia but they had died out by about 10,000 BCE leaving just a remnant population isolated and trapped on St. Paul's Island. Extinction elsewhere had probably been due to a combination of climate change and human predation. Unlike the Indian and African elephants, these mammoths were adapted to cold climate so heat retention and conservation would have been important attributes. However, when the climate got warmer at the end of the Ice Age, like other cold-adapted large mammals, these adaptations became maladaptations.
In Beringia, as the climate warmed, the ice sheets shrank and sea levels rose, a population of mammoths became isolated and clung on there for about another 5000 years. This population would probably have needed a lot of fresh water because of their now maladaptation to Ice Age conditions and this proved to be their Achilles heel. The climate not only became warmer but also became drier and their water supply ran out. And that was that.
In an illustration of the unplanned, blind, uncaring nature of evolution, a species which had taken millions of years to evolve and adapt to the Ice Age had been forced down an evolutionary cul-de-sac and evolution doesn't have a reverse gear. The mammoths had become over-specialised and so unable to adapt quickly enough for the new situation. They had nowhere to go but over the cliff to which their species had been heading.
No doubt creationists will have thought up a reason for this because their supposedly omniscient designer will not only have seen this coming but will have been responsible for it happening. It must therefore have intended this extinction and merely delayed it for a few thousand years on St. Paul's Island only to deprive the remaining mammoths of the large supply of fresh water it had designed them to need earlier on.
No doubt we'll have lots of excuses, if this news isn't ignored altogether, but never anything resembling a scientifically testable explanation nor any explanation which resembles the actions of an intelligent designer.
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