a bonobo humanity?

I’ve been reading this entertaining book on dinosaurs by the curmudgeonly controversialist Brian Ford, who insists that dinosaurs were largely aquatic. I know about as much about dinosaurs as Trump knows about government, so I’m not going to wade into the central debate, if there is one (most palaeontologists dismiss Ford’s claim out of hand), but there’s so many items and assertions here worthy of further investigation that I’m bewildered by choice. So I’ve decided that, since there’s so much interest in current climate change and what it might mean for the future of various biosphere life-forms including ourselves, I’ll spend a bit of time researching what’s known about the climate, and the atmosphere, during the Cretaceous period – a very long time-span indeed from a human perspective, stretching from around 145 million years ago to 66 million years ago. It seems to have have been very different then (assuming that 80 million years of weather can be encapsulated in one description) from what it is now, and yet life was thriving – so why worry?

Well, life then was life as we don’t know it now – though, interestingly, many plants of the period still exist today, including plants from even earlier, such as gingkos and horsetails. In fact, the Cretaceous saw the emergence of flowering plants (angiosperms) in great numbers, and this favoured a rise in dinosaur numbers and types. The climate generally was warm, wet and tropical, and according to NASA climate scientists, carbon dioxide levels were at 1000 ppm (in the middle Cretaceous, around 110 mya), compared to around 410 ppm today. Sea levels were around 300 feet higher than today, and surface temperatures averaged 27 degrees celsius compared to about 15 at present. It’s likely that no ice existed anywhere on the planet.

So why so much CO2, and how did it come to drop? To take the second question first, at this time, the continents weren’t where they are today. Some 90 mya India began a rapid movement away from Madagascar towards Asia at a rate of 15-20 cms per year. It collided with the Asian plate some 55-50 mya, creating the Himalayas, and silicate weathering began, resulting in the incorporation of CO2 into carbonate, which washed into the ocean and was buried. The surface temperature started to drop with CO2 levels, which came down to an inter-glacial atmospheric concentration of about 280 ppm in CO2. Once that concentration got down to 450 ppm the Antarctic ice sheet began to form, and the Greenland ice sheet started at around 400pm, all of which is highly relevant to today’s climate situation with its rise in CO2 levels.

As to the first question, plate tectonics and related volcanic emissions appears to provide most of the answers. It’s believed, in fact, that CO2 levels were as high as 4000 ppm during the Cambrian period, over 500 mya (and at their lowest at 180 ppm during the Pleistocene glaciation a little over 2 mya).

None of this, of course, comes close to answering questions about dinosaur lifestyle, but I do note that Brian Ford is an outlier not only for his aquatic dinosaur hypothesis. He also questions, indeed trashes, the dinosaur extinction-by-meteor story, and argues that the sky was probably orange-yellow, to our perception, at the time of the dinosaurs. All of this is contrary to generally accepted science, so he’s rather unlikely to be correct. Having said that, questions about how some of these incredibly massive sauropod beasties managed to get around and consume enough food to maintain themselves – these still appear to be unanswered to a large degree. Hopefully somebody will build a time machine soon.

References

Too big to walk, by Brian Ford, 2018

https://www.livescience.com/44330-jurassic-dinosaur-carbon-dioxide.html

PSW 2404 Satellites, Dinosaurs, Milankovitch Cycles, and Cretaceous Earth | Compton Tucker (video)

What was the climate like during the age of Dinosaurs? / Benjamin Burger (video)

https://ask.metafilter.com/194137/What-color-was-the-sky-millions-or-billions-of-years-ago

https://www.sciencemag.org/news/2019/10/sauropods-grew-big-munching-superfoods-sturdy-beaks