Hot Earth Dreams: What if severe climate change happens, and humans survive? by Frank Landis

Author:Frank Landis
Language: eng
Format: mobi, epub
Published: 2015-11-13T04:30:00+00:00

One other PETM phenomenon has been unearthed: Wyoming dwarfing. After the “carbon isotope excursion,” (CIE) the anomalous peak of carbon-13 that marks the start of the PETM, the animals got smaller. This was seen both in mammals, whose estimated mass decreased by around 30 percent (Gingerich 2006), and in the burrow diameters of things like earthworms and crayfish, which also decreased by 30-46% (Smith et al. 2009). In fact, the smaller size of fossils was among the first evidence that something was very odd at the boundary between the Paleocene and Eocene, the PETM.

So far as I can tell, this has only been seen so far in Wyoming, apparently because that’s where the best fossils for this period are, but there’s no reason to think that it wasn’t a widespread effect. It’s also not clear how it long took species to shrink. Some dwarfed fossils date to 10,000 years after the CIE, some almost immediately after (Smith et al. 2009), and the dwarfing seems to have lasted for the length of the PETM, with animal fossils returning to their pre-PETM size after the PETM was over.

What happened? Speculation generally revolves around increased CO2 causing plants to produce less food for animals, and drier soils favoring smaller earthworms. I’d also suggest that the soil-plant mismatches and rapid climate fluctuations mentioned above are problems for plants, problems that could certainly generate less food for the animals that eat them. Other issues, like diseases, could also contribute, since shortening lifespans favors animals that mature when younger and smaller, driving evolution towards genetic dwarfing (Migliano et al. 2007).

There’s no reason to think that the High Altithermal won’t cause shrinkage of many animals, and this will probably include humans. To provide a reference, the average US male and female, age 20-29, weighed 88.7 kg (195.5 lb) and 75.4 kg (166.2 lb) from 2007-2010 (Fryar et al. 2012). Yeah, we’re fat. Shrink us 30% and the average American man and woman would weigh 62.09 kg (136.6 lb) and 52.8 kg (116.1 lb), or about what people now weigh on average in much of Asia. Shrink modern Asians by 30% and people start getting into the body range of modern pygmies, groups where the men are five feet tall and under.

So yes, the future is downsized, as well as nasty and brutish at times, and we’re likely to remain short through the entire Altithermal. Adaptation bites sometimes, doesn’t it?

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