Wednesday 30 September 2020

Arsenic and old lakes

Microbial Mats (purple) at Laguna La Brava Chile
From Visscher et al. 2020 CC BY 4.0

Atmospheric oxygen was not plentiful until the Great Oxidation Event yet life appeared much earlier during the Archean Eon (more than 3 gigayears ago). One suggestion has been that  arsenic acted as an electron donor to drive photosynthesis in early life forms.

A new paper by Visscher et al. shows how this might have worked. They investigated microbial mats from Laguna La Brava in northern Chile. These survive under hypersalinic and anoxic conditions by using arsenic and sulphur as electron donors.

A parallel is drawn with the Archean lakes of the Tumbiana Formation where lithified microbial mats are found. 

Thursday 3 September 2020

Kindred or cavemen

 



Neanderthals gained prominence in the Eemian interglacial some 130 thousand years ago and survived several cold and warm periods before disappearing 40 thousand years ago. So they have a much longer history than modern humans. What were they like? Becky Wragg Sykes gives some answers and where answers are missing supplies well argued speculation. Often speculation is backed up by comparison with recent human hunter-gatherers.

The strength of this book lies in covering so much ground. For example I have followed the ancient DNA closely, know a bit about fossil finds, but have steered clear of lithics (e.g. bifaces formerly known as stone axes). Yet there are so many more of these remains and new methods to get the most out of them. They are key to understanding the Neanderthals skills and way of life.

Importantly Neanderthals did not just huddle in caves between hunting woolly mammoths. They also lived through warmer periods and hunted horses and other prey. They were geographically diverse too living in the warmer climes of Iberia and across Asia to the Altai mountains in Mongolia.

It is common knowledge that Neanderthals mated with humans and with the enigmatic hominins called Denisovans about whom we know very little. Sykes thinks they may have been so like us that sex could have been consensual. She is a great fan of Jean Auel (whose books I too have read).

My enthusiasm waxed and waned with every chapter. I could not quite get accustomed to the author's style of writing. Apart from lithics I did not learn an awful lot. But perhaps the book was not written for me.


This one was more my style.