Recently I've been watching a lot of PBS Eons and Ben G Thomas on youtube and inspired by them, and my lifelong love of the history of life on earth, today we're talking about 6 animals we almost got to me. From an 8 metre long Sea cow, to giant sloths, the poster boy that is the dodo. Looking at animals that went exitinct in the more modern history of humans at that were at their peak in the late prehistoric era. Animals that may have made it till today had conditions been slightly different.
Today we reach over 1400 extinction a year, and over 99% of all species that have ever existed on earth are currently extinct. But in today's world human activity accounts for most of the extinctions and learning about how more recent extinctions happened can help us to prevent more, and save animals we still have with us.
This list is actually 3 animals and two birds... but that didn't have quite the same ring to it.
First up is the animal that inspired me to make this list. Stellar's sea cow (Hydrodamalis gigas) is an 8m long sea cow, its closest relative being the long dugong, that went extinct in the late 1700s just 27 years after it was discovered and documented by Europeans.
Almost everything we know of this amazing creature comes from the writings of Georg Wilhelm Steller, who got shipwrecked on an island in the Bering sea in 1741. Thought to be a monogamous and very social animal, weighing from 4500 to 5900kg[1], and living in family groups. It had thick blubber under the surface of it's skin and lived life floating at the surface shallow water near coastlines feeding on algae kelp.
But it was this huge size, social grouping, lack of fear for humans and low mobility that also was their last downfall, Russian sailors who were travelling around the bearing sea, hunting sea otters for their fur, were believed to have used the Steller's Sea cow as a source of food. Hunted at over seven times the sustainable limit[2]. They were gone from from copper island by 1754 and Bering Island, their last home, by 1768[3]
Though it is thought the giant sea cow may have been on its way to extinction before the Russians arrived, as it was already endangered. With fossils found from Monterey bay in California to Honshu in Japan it was likely hunted by prehistoric humans first.
The Stellar Sea Cow really demonstrates the impact that humans can have when overexploiting resources, especially ones that seem like easy pickings.
Next up we have the poster child of extinction, flightless bird the dodo. This one metre tall bird lived on the island of Mauritius, it succumbed to extinction in the late 17th century (1662) less than a century after its discovery by europeans. First believed to be related to many different birds, its actually a part of the same family as the pigeons with its closest living relative being the very colourful Nicobar pigeon [4].
Despite being the poster child, accounts of the dodo vary quite a bit. With illustrations of the bird depicting being the primary evidence for its appearance, and little being known about their life. Considered fat, stupid clumsy birds, destined for extinction, but due to their relationship to pigeons that is unlikely the case [5]. They lived a blissful predator free life on Mauritius with no fear and plenty of food. So its lack of fear of humans and flightless ness wasn't down to stupidity but simply a lack of necessity.
Again its lack of fear humans, as well as its inability to fly left it very vulnerable, hunted by sailor and invasive species. This and its massive loss of habitat led to its extinction, with many being put into captivity, fed and fattened up to be used as food.
This quick loss after its discovery is what has made it the face of extinction today as it was one of the first animals to really highlight the issue of human involvement in the loss of entire species. Its role in Alice in Wonderland helped to fix it in that place. And like the Steller's sea cow it was just too easy pickings for humans.
The next animal I'm talking about is not one distinct species but an extinct group in mammalian superorder Xenarthra. Most of these sloths died out in the prehistoric era and they had ranges from mountain dwelling who lived in caves to low lying woodland and forests, and even sub aquatic giant sloths such as Northrotheriidae who would have had to fend off carnivorous whale species.
These were an incredibly diverse range of sloths weighing more than an elephants and with a range across the North and South of the Americas. With a medium sized sloth being about 3m from snout to tail these really were giants. And in the 20th century dung that looked "fresh" sparked expeditions to find the living mammal[6], though these were in fact over 10,000 years old. But you can forgive their mistake, some skeletons are found with skin and hair still preserved.
The extinction of many of these sloths came at a time of climate change, when the ice age ended 12,000 years ago, and its debated as to whether it was the climate changing or humans that helped these sloths meet their demise. And it's likely we did hunt them[7]. But one group of sloths on the Antilles lived much longer than their relatives, possibly until around 1550BC[8]. In the Caribbean they were found to have lived until 4,4000 year BP, 1000 years after humans arrived.[9]
The thing is, though climate change happened around the same time, wherever humans arrived large mammals' numbers dwindled into extinction.Today only 10% of sloth species remain and it is likely we at least played a part in the extinction of these megafauna. These days all we have left of the sloths are the two toes and three toed sloths of south America, as well as some pygmy species, which are all arboreal species which hang from trees, the oddballs of their sloth family. Not exactly easy pickings, or a very big lunch, for human hunters.
But one thing we can thank the Giant sloth for the continued existence of avocados. But I'll leave that for another post.
These days when you think of weird and wonderful creatures, including some giant and flightless bird species, you might go straight to Australia and New Zealand, and thats' where this next giant bird group came from. The Giant Moa of New Zealand.
There were nine species of this bird, reaching heights of 3m (10tf) [10], and getting as small as chickens. Now when talking about giant flightless birds your first thought might be Emu's and Ostriches, or even the Kiwi but the Moa's closest living relative is actually a small bird with flight, the Tinamou of South America[11]. And the Kiwi's closest relative is the giant and extinct elephant bird that lived in Madagascar![12] So several species of giant flightless birds all lost their ability to fly, and became large, independently. A nifty bit of convergent evolution.
With a lack of predators in New Zealand, losing the high energy ability to fly and instead growing to gigantic proportions meant filling a different niche. They were a plant eater in New Zealand's forest, a dominant species with only the Haast's Eagle, the largest eagle ever to have existed, as their predator
And the reason for these bird's extinction? You guesses it, humans, they likely became extinct in around 1300 AD just 100 years after humans arrived. Though there were unconfirmed sightings in the 18th and 19th centuries. Their predators the Haast's Eagle also went extinct around a similar time due to their prey being hunted by humans. [13][14]
Dwarf Elephants
Large animals on islands have a tendency to get really small, I mean it makes sense, less space and less food means more competition for larger animals and so getting smaller means your species is more likely to survive. This is exactly what happened to the dwarf elephants, prehistoric members of Proboscidea, which includes todays African and asian elephants.
Dwarf elephants evolved on islands including the mediterranean islands, having heights of 1.5-2.3m. Fully grown, they were the size of a juvenile Asian elephant. These islands became connected and disconnected time and time again giving rise to several species of dwarf elephants of varying sizes.
Dwarf elephants are also thought to be the reason for the myth of the cyclops, due to their skulls having one very large opening in the front that could have been an eye socket and are found in caves on costal regions of Italy and Greece.[15]
There were even dwarf mammoths, found exclusively on Saint Paul Island which survived until 6000BC [16]. Some of the last surviving mammoth populations they reaches heights of just 1.5-2m [17].
The extinction of these tiny elephants is thought to be from the arrival of humans on many of these islands but it is still debated and this hasn't been proven. They're a tiny mystery
There are also modern elephants in Borneo, Malaysia and Indonesia that are often referred to as pygmy elephants. However, these elephants are, on average, not much smaller than other asian elephants; 72-90%; 2-3m. [18]
And that's it for these five animals, sadly their demise was likely down to humans, but it does tell us how precious animal life is and how quickly we can lose it if we're not careful and don't try to protect it. We haven't quite learnt from the past yet, but there is still time.
I had a lot of fun researching and writing this post, it's not my usual kind of piece here but I may do more, I hope you enjoyed it! Do you have a favourite extinct animal?
References:
[1] - Encyclopedia of Marine Mammals, Second Edition. Edited by William F. Perrin, Bernd Würsig, J.G.M. Thewissen
[2] - Turvey, S. T., & Risley, C. L. (2006). Modelling the extinction of Steller's sea cow. Biology letters, 2(1), 94–97. doi:10.1098/rsbl.2005.0415
[3] - S. O Macdonald, & Joseph J Cook (2009), Recent Mammals of Alaska
[4] -Heupink, T. H., van Grouw, H., & Lambert, D. M. (2014). The mysterious Spotted Green Pigeon and its relation to the Dodo and its kindred. BMC evolutionary biology, 14, 136. doi:10.1186/1471-2148-14-136
[5] -Gold, M.E.L., Bourdon, E. and Norell, M.A. (2016), The first endocast of the extinct dodo (Raphus cucullatus) and an anatomical comparison amongst close relatives (Aves, Columbiformes). Zool J Linn Soc, 177: 950-963. doi:10.1111/zoj.12388
[6] - PATAGONIA; Hesketh-Prichard's Stirring Tale of Exploration in the Far South.
[7] - Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America
[8] - R. D. E. MacPhee, M. A. Iturralde-Vinent, Osvaldo Jiménez Vázquez "Prehistoric Sloth Extinctions in Cuba: Implications of a New “Last” Appearance Date," Caribbean Journal of Science, 43(1), 94-98, (1 June 2007)
[9] - Asynchronous extinction of late Quaternary sloths on continents and islands. , , , , , , ,
[10]- https://www.britannica.com/animal/moa
[11] -Morten E. Allentoft, Nicolas J. Rawlence, Moa's Ark or volant ghosts of Gondwana? Insights from nineteen years of ancient DNA research on the extinct moa (Aves: Dinornithiformes) of New Zealand, Annals of Anatomy - Anatomischer Anzeiger, Volume 194, Issue 1, 2012
[12] -Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution By Science : 898-900
[13] - , Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test, and Implications Science : 2250-2254
[14] - Milberg, P. and Tyrberg, T. (1993), Naïve birds and noble savages ‐ a review of man‐caused prehistoric extinctions of island birds. Ecography, 16: 229-250. doi:10.1111/j.1600-0587.1993.tb00213.x
[15] - The first Fossil Hunters: Dinosaurs, Mammoths, and Myth in Greek and Roman Times; Adrienne Mayor, 2011
[16] - Dale Guthrie, R. Radiocarbon evidence of mid-Holocene mammoths stranded on an Alaskan Bering Sea island. Nature 429, 746–749 (2004) doi:10.1038/nature02612
[17] - Semprebon, Gina & Rivals, Florent & Fahlke, Julia & Sanders, William & Lister, Adrian & Göhlich, Ursula. (2016). Dietary reconstruction of pygmy mammoths from Santa Rosa Island of California. Quaternary International. 406. 10.1016/j.quaint.2015.10.120.
[18] - http://animalia.bio/borneo-elephant
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