Maybe we've just been measuring sleep wrong
After reading the discussion of the traditionally accepted 8 hours of sleep a night versus a possible 6.5 hours as optimal for maximum brain volume, I wonder if the difference may be linked to our measurements. Before we had smart devices with sleep trackers, we would generally assume that the time we went to bed until the time we woke (perhaps minus a dozing-off period) was our total sleep time. Smart trackers measure when we wake up over the course of the night, for short periods that we may not be aware of. I have noticed that my sleep duration as defined by a smart device is often a fair bit less than the amount of time between going to bed and waking up (4 November, p 10).
On the vexed question of the origin of life on Earth (1)
When considering the origin of life on Earth, note that it all runs on the same power system of ion gradients across a membrane. As this is universal, it must date back to a universal common ancestor (4 November, p 36).
How could such a system have developed on early Earth with only water, rocks, hydrogen and carbon dioxide to work with? The logical answer is that life arose where there was a natural ion gradient that could be exploited and alkaline hydrothermal vents, which you briefly touch on, are that place. Exploration of this idea has led to a lot of work, particularly by groups in Europe, which have produced a large body of biochemically sound literature.
On the vexed question of the origin of life on Earth (2)
There was no mention of the admittedly unfashionable panspermia proposal, the idea that life came from beyond Earth. While it doesn’t explain the origin of life, it could, if true, mean that the first organisms didn’t come into being here, but in a different environment. In this hypothesis, life on Earth began not when the environment became conducive to its creation, but when it became compatible with some existing life forms that fell from the sky.
Pixelated space-time might explain a lot
The concept of quantised space-time may be the key to understanding the multiverse 鈥� and the requirement that the plethora of universes must display a wide range of properties that fortuitously result in a limited number being relatively stable and life-friendly (28 October, p 30).
If the fundamental constituents of space-time were to consist of a mixture of “pixels”, one could imagine that each universe had different proportions determined at its birth, with consequent variation of properties. The fundamental particles may thus be common to all, but they may interact differently due to the nature of the background space-time in which they exist.
My pet cat was like a high-ground-seeking spy chimp
Your article about chimpanzees seeking higher ground for tactical reasons reminds me of one of our cats. He would run upstairs for a better look if he saw something interesting in the back garden. What was curious was that not only did he have the nous to do this, he also had the orientation sense to know which rooms gave him the best vantage point (11 November, p 19).
Heat pumps: call off the bulldozers
John Kitchen pushes the idea that Victorian homes (broadly) aren’t suitable for heat pumps, suggesting they may have to be bulldozed. Heat pumps simply output heat, and physically can heat any building, full stop. It is true that cost, unsightliness and regulations may be obstacles, but these are artificial constraints. Equally, all buildings are far cheaper and easier to heat if well insulated, although the cost of doing so may not be justifiable in purely monetary terms. But we don’t need to bulldoze any homes (Letters, 11 November).
Protect us from Martians, and them from us too
You published a timely article about preserving us from the possibility of being wiped out by Martian microbes brought back to Earth in study samples. I hope sufficient steps are being taken to prevent Earth microbes from contaminating Mars and elsewhere that we visit (4 November, p 21).
It would be a tragedy to wipe out life forms before we even meet them, especially in the name of science. Am I right in thinking that a consignment of Earth tardigrades crashed onto the moon recently? Oops!
Food additives aren't always unnatural
I appreciate the more realistic approach to so-called ultra-processed foods in your recent article, but would like to make a couple of comments (28 October, p 40).
Emulsifiers aren’t all potentially harmful “additives” as implied. Many occur naturally in food we eat, such as lecithin (E322), found in egg and soya beans, and mono- and diglycerides of fatty acids (E471), produced during the normal digestion of triglyceride fat. The human body also produces its own emulsifiers in bile, which assist in fat absorption. The emulsifiers in egg allow us to make mayonnaise and are also an important source of choline.
Acrylamide isn’t an additive as such, but a natural toxin potentially produced during baking, be it at home or in a factory. However, manufacturers have been taking steps to reduce the amount of this, as well as other potential toxins associated with poor cooking practices, such as trans-fatty acids and polycyclic aromatic hydrocarbons. Since most consumers cooking at home have no knowledge of these toxins or how they are formed, this is an example of how so-called ultra-processed foods might be safer than home-prepared equivalents.
We may be at the beginning of The End
Further to Bryn Glover’s call for names for the opening chapter of the proposed next geological epoch 鈥� the human-induced Anthropocene 鈥� I would suggest that an appropriate title for its first age might be “The End” (Letters, 4 November).