Over-kill, over-chill, or over-ill?
Why a mass extinction at the end of the Ice Age?
The post-Flood rapid Ice Age was quite different from the multiple ice ages that uniformitarian scientists propose. An Ice Age after the Flood is a logical conclusion from the unique climate conditions that existed immediately after the Genesis Flood.
The post-Flood Ice Age has strong explanatory power. It predicts, for example, the ‘disharmonious associations’ that puzzle secularists. That is, the odd mix of warm and cold climate plants and animals living during the Ice Age. As we showed,1 these result from the equable climate (mild winters, cool summers) unique to the post-Flood Ice Age.
It also answers another Ice Age mystery, among many others for uniformitarians. Namely, why there was a mass extinction at the end of the Ice Age.
The mass extinctions
As the ice sheets were melting, and more space for vegetation was opening up, a global mass extinction of megafauna—large animals over 44 kg (100 lb)—occurred (figures 1 to 6).
How many large creatures went extinct? Evolutionary estimates of the percentages have changed over the years. However, in general about 65% of the megafauna went extinct globally at the end of the uniformitarians’ ‘last’ ice age (table 1).
Some 97 species of birds in the world also went extinct at the end of the Ice Age. Many of these were types, e.g. scavengers, significantly dependent on the existence of the large Ice Age mammals.2
Uniformitarian mass extinction hypotheses
Of the many hypotheses for these extinctions, the three main recent ones have been labelled:
(1) Over-kill, where man is responsible for the mass extinctions via hunting.
(2) Over-chill, in which climate change caused the mass extinctions.
(3) Over-ill, caused by diseases and pests, such as rats, spreading around the earth, facilitated by man.
Each of these hypotheses has strengths and weaknesses. This is why the cause of the end-Ice-Age mass extinctions is so hotly debated and unresolved. All sides are deeply entrenched in their positions; the sometimes bitter debate has lasted 200 years, and no solution seems in sight.
Over-kill strengths and weaknesses
Over-kill advocates emphasize the ‘timing’ of the extinction coinciding with man entering a continent, especially Australia and the Americas. In the secular view, the Ice Age (the only one, in reality) was merely the ‘last’ of about 50 prior ones of various intensities.3 Thus, they claim, climate change cannot be the cause. So by the process of elimination, they argue that the last ice age was ‘special’ because of colonization by man.
However, on some continents the timing of man’s arrival does not coincide with the extinctions. In the uniformitarian scheme, Eurasia and Africa do not fit ‘over-kill’. They had low numbers of extinctions while man lived alongside the megafauna for supposedly hundreds of thousands of years. So, its advocates need to, and do, try to explain this away. Moreover, the timing of man’s entry and of the extinctions in Australia and the Americas depend strongly on precise dating. History has shown that their ‘dates’ for events have changed for various reasons. Circular reasoning plays a part in dating the extinctions to exactly when man arrived. Further research has pushed this arrival to increasingly older dates. James Kennett and others, who advocate extinction by an end-Ice-Age comet or asteroid impact, say: “Out-of-sequence 14C dates are a common dating problem that is solved by discounting outlying young dates.”4 In other words, dates are excluded if they do not agree.
Over-chill strengths and weaknesses
Over-chill advocates point out that only small populations of man entered Australia and the Americas. Armed mostly with spears and stone knives, they could not wipe out so many large mammals, most of which were not their quarry.
The climate was radically changing at the time, so they blame the extinctions on climate change. This works well for North America at the end of the Ice Age. However, South America supposedly had a weak end-Pleistocene climate change, and yet that continent was hit the hardest by 83% extinctions.
Over-chill advocates rightly point to Africa and Eurasia as contradictions to over-kill. They point out that globally there are very few associations between human archaeological sites and megafaunal associations—way too few to provide evidence for over-kill. But over-kill advocates counter that such low numbers of man/megafauna associations are what they ‘expect’. They argue that the older the associations, the faster they should disappear from the archaeological record.5
Most secular scientists have rejected over-ill as implausible because there is little, if any evidence, to support it. Multiple random diseases, which are in any case most often species-specific, would have affected only local to regional populations at best. This wouldn’t explain the hemisphere-wide extinctions of some animal groups.6 Some sort of global hyper-disease affecting many different species has been proposed. However, it is difficult to imagine any disease selectively killing off large animals while sparing both man and smaller animals. The only possible modern global-disease analogue, the West Nile Virus, could not selectively target the large animals and generally provides no support for over-ill.
Secular scientists perplexed
Monjeau et al., who have attempted a compromise between over-kill and over-chill, admit there is no agreement:
Resembling the fascination for crime stories, speculations about the causes of terrestrial mammal extinctions in the Quaternary have been at the center of one of the most exciting and unresolved debates in contemporary biology. For the last two centuries, hundreds of papers have been written on this topic, proposing a range of explanations. … and to this day there is no agreement forthcoming … .7
The post-Flood Ice Age solves the mystery
The post-Flood Ice Age explains the megafauna-mass-extinction mystery. As shown in a previous article, the early to middle part of the Ice Age was characterized by a mild, equable climate with little seasonal contrast.1 Precipitation was much more abundant than it is today because of the high rate of evaporation from warm oceans. Animals thrived in this climate where food and water were plentiful. The diversity of mammal populations in Siberia has been described by some scientists as similar to the famed Serengeti of Africa.
But the Ice Age climate was dynamic. By its end, the summers grew warmer, and the ice sheets began to melt, but the winters grew even colder than they are today. These changes brought about large seasonal contrasts. In the far north, less dense glacier meltwater flooded over the top of the salt water of the Arctic Ocean, the northern Pacific Ocean, and the northern Atlantic Ocean. It froze rapidly. The remaining surface of the ocean became even colder than it is today. There was no evaporation from areas of sea ice, and the colder oceans produced less evaporation. So, there was less precipitation over the land. This new weather dynamic resulted in widespread drought.
The land in the tropical latitudes would have warmed at the end of the Ice Age, after the once abundant post-Flood volcanism had decreased (fewer eruptions = fewer aerosols to cool Earth by reflecting sunlight back into space). The temperature difference between the tropical and the polar latitudes would have been much greater than today.
The huge temperature difference between the cooler air above the ice sheets and the warmer air of the lower latitudes produced much stronger winds than today. By the end of the Ice Age, fierce winds swept over large areas picking up dirt and sand. Abundant sand and wind-blown silt, loess deposits, are associated with the Ice Age. The fierce wind and drought at the end of the Ice Age would also have helped fires to rage across large areas.
Although some animals, such as the woolly mammoths, were conditioned to cold winters, most were not, unlike what secular scientists think. When the winters became much colder, most were greatly stressed. Drought resulted in less food, which would have had a greater impact on the larger animals and the slower-reproducing animals.
Less forage, colder winters, drought, strong winds, and fires combined to cause the mass extinctions. Each continent experienced its own unique variations of these factors. Drought likely wiped out the large animals in Australia and South America. The vast majority, if not all, of the mass extinctions were caused directly or indirectly by ‘over-chill’.
Only one Ice Age
The post-Flood Ice Age explains many mysteries confounding uniformitarian scientists. One of the problems it solves is why there was a global mass extinction of megafauna at the end of the Ice Age. Further, according to uniformitarians, of the dozens of alleged ice ages they claim, only the ‘last’ one saw mass extinctions. This is strong evidence that there was only one Ice Age, which is consistent with the aftereffects of the biblical Flood.
References and notes
- Oard, M.J., A strange mix of plants and animals during the Ice Age, Creation 42(4):39–41, 2020. Return to text.
- Tyrberg, T., The Late Pleistocene Continental Avian extinction—an evaluation of the fossil evidence, Oryctos 7:249–269, 2008. Return to text.
- Walker, M. and Lowe, J., Quaternary science 2007: a 50-year retrospective, J. Geological Society London 164:1073–1092, 2007. Return to text.
- Kennett, J.P. et al., Reply to Holliday and Boslough et al.: Synchroneity of widespread Bayesian-modeled ages supports Younger Dryas impact hypothesis, Proceedings of the National Academy of Science 99:E6723, 2015. Return to text.
- Surovell, T.A. and Grund, B.S., The associational critique of Quaternary overkill and why it is largely irrelevant to the extinction debate, American Antiquity 77(4):672–687, 2012. Return to text.
- Boulanger, M.T. and Lyman, R.L., Northeastern North American Pleistocene megafauna chronologically overlapped minimally with Paleoindians, Quaternary International 85:35–46, 2014. Return to text.
- Monjeau, J.A. et al. The controversy space on Quaternary megafaunal extinctions, Quaternary International 431:194, 2017. Return to text.
- Barnosky, A.D. et al., Assessing the causes of Late Pleistocene extinctions on the continents, Science 306:70–75, 2004. Return to text.
- Faith, J.T., Late Pleistocene and Holocene mammal extinctions on continental Africa, Earth-Science Reviews 128:105–121, 2014. Return to text.