Readings: Earth's Ice, Neanderthal Women, Indian Monsoons

Some good stuff from the past few weeks.

1) How much of the Earth's Ice is Melting? Sid Perkins writes about the variety of methods of estimating ice loss from the high latitudes. These methods are showing where and how much melting is taking place, in turn, helping scientists make predictions of future sea level rise. The overall scenario is rather gloomy. 

2) The Lives of Neanderthal Women. "Archaeology is no exception to biases against women’s interests across science and the humanities". Archaeologist Rebecca Wragg Skykes expertly constructs a picture of what the lives of Neanderthal women might have been like.

3) Indian Monsoon Across Millennia. Stalagmites from a cave in Meghalaya, NE India are giving paleoclimatologists information about monsoon variability over a thousand years. Their geochemistry points to periodic deadly droughts that coincide with phases of major social and political turmoil in India. Paper authors Gayatri Kathayat and Ashish Sinha describe their research. 

 

Lessons From A Hot Past

This short editorial published recently in Nature Geoscience is worth reading and thinking about. It summarizes our findings of past climate change and how earth systems such as sea level, glaciers, and the biosphere responded to these climate swings. 

Reconstructing temperatures going back to the Eocene (~50 million years ago) and later in the Miocene (~ 15 million years ago) reveal a very different world. These finding do come with a caveat. The rates of change are averaged over thousands of years, while we today stare at an unfolding catastrophe in our lifetimes. 

There is data though from more recent times that can tell us in finer temporal detail how climates fluctuated. Carbon dioxide trapped in Antarctica ice sheets points to changing atmospheric composition on a centennial scale and tree ring data informs us about seasonal changes in rainfall.

The current level of CO2 in the atmosphere of about 415 ppm (parts per million) are the highest since the Pliocene, more than 3 million year ago. We are also pumping CO2 at rates which are unprecedented in geologic memory, a shift from about 280 ppm to our present levels in just about 150 years The past may not provide a perfect analogue for the rapid changes we are experiencing, but it does send us a sobering warning that civilization's envelopes of comfort will be breached not so far in the future.

Nature Geoscience Editorial: Lessons From A Hot Past.

What Geology Tells Us About Climate Change

Set aside an hour and read this article.

Geological Society of London Scientific Statement: what the geological record tells us about our present and future climate.

It really is an excellent explanation. 

Wishing readers a very Happy New Year! 

Readings: Human Evolution, Ice Ages, Brains In Digital Age

Some interesting articles to read:

1) How did Homo sapiens evolve in Africa? Did one population branch off and evolve all the traits of 'modern humans' in isolation or were there several populations spread across the continent which at times evolved in isolation but periodically met and exchanged genes and cultural practices, resulting in a gradual coming together of the constellation of traits we see in us? Recent findings based on the fossil and tool record is pointing to the latter process.

The search for Eden: in pursuit of humanity’s origins by Robin McKie.

2) How do variations in the earth's orbit influence the growth and decline of glacial and interglacial periods? Excellent review article on the factors controlling climate change over the past 2.5 million years.

Tying celestial mechanics to Earth’s ice ages by Mark Maslin.

3) How is the human brain coping with the information deluge of our times?

Extract:

" Humans, of course, forage for data more voraciously than any other animal. And, like most foragers, we follow instinctive strategies for optimizing our search. Behavioral ecologists who study animals seeking nourishment have developed various models to predict their likely course of action. One of these, the marginal value theorem (MVT), applies to foragers in areas where food is found in patches, with resource-poor areas in between. The MVT can predict, for example, when a squirrel will quit gathering acorns in one tree and move on to the next, based on a formula assessing the costs and benefits of staying put — the number of nuts acquired per minute versus the time required for travel, and so on. Gazzaley sees the digital landscape as a similar environment, in which the patches are sources of information — a website, a smartphone, an email program. He believes an MVT-like formula may govern our online foraging: Each data patch provides diminishing returns over time as we use up information available there, or as we start to worry that better data might be available elsewhere.

The call of the next data patch may keep us hopping from Facebook to Twitter to Google to YouTube; it can also interfere with the fulfillment of goals — meeting a work deadline, paying attention in class, connecting face-to-face with a loved one."

There is some sensible advice at the end on how to build healthier habits and manage our dependencies on technology.

How Our Ancient Brains Are Coping in the Age of Digital Distraction by Kenneth Miller.

Readings: Erectus SE Asia, Devonian Fossil Forest, Archean Iron Formations

Some selected readings:

1) New dates of Homo erectus from Ngandong Java shows late surviving populations until 117,000 to 108,000 years ago. A short clean summary by Razib Khan on SE Asian hominin diversity.

Southeast Asia during the Eemian was a hominin paradise.

Paper: Last appearance of Homo erectus at Ngandong, Java, 117,000–108,000 years ago.

2) Exquisite preservation of one of the earliest forests from the Mid Devonian ( ~385 million years ago) of New York containing a modern looking root system.

Paper - Mid-Devonian Archaeopteris Roots Signal Revolutionary Change in Earliest Fossil Forests.

Write up : The World’s Oldest Forest Has 385-Million-Year-Old Tree Roots.

3) Before around 2.3 billion years ago there was very little oxygen in the atmosphere. This was a time before the evolutionary invention of oxygenic photosynthesis wherein bacteria harvest electrons from H2O and release oxygen as a byproduct. Instead, during this time another photosynthesis pathway known as photoferrotrophy was prevalent. Here, bacteria use light and ferrous iron (Fe+2) to fix CO2 as biomass, releasing ferric iron (Fe+3) as byproduct. This ferric iron then accumulated to form large iron deposits. But these deposits lack organic matter. How to explain this if the iron was being produced from a biomass? Scientists point to a role of silica. At that time the oceans were saturated in free silica. Experimental work shows that in the presence of free silica cell surfaces repel iron hydroxides, thus creating a source of organic matter free iron deposits. This organic matter then was acted upon by methane producing microbes. The methane released kept the temperature of the earth warmer than it would have been under a dim early sun.

Fascinating story of the feedback between geology and evolution.

Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans.