Decline and fall
Like many readers, I’m sure, I read the article on the decline of phytoplankton and the cost of carbon fixes with a sense of dread (7 April, p 42). It reminded me of historian Paul Kennedy’s theory of imperial overstretch.
In his 1987 book The Rise and Fall of the Great Powers, this Yale professor of economic history demonstrated that empires tend to expand until (basically) the amount that can be raised in taxes is lower than the cost of enforcing taxation, and the economy collapses.
Has the human empire reached the point at which the work needed to repair and maintain the ecology is already greater than our economic ability to do it?
And is this an inevitable result of the development of a technological culture?
If so, it would explain why SETI, the search for extraterrestrial intelligence, listens for signs of other such civilisations but hears only silence.
Salt! salt!
Reviewing the book Taste What You’re Missing, Catherine de Lange raises the question of why we do not crave salt as we do the equally essential water (24 March, p 54). But I do crave it, in exactly the same way; in fact, my cravings make no distinction.
When I go for a long walk on a hot day, the result is, not surprisingly, a salt-encrusted brow and a chronic thirst which persists for several days – long after I am rehydrated – unless I drink lightly salted water to stop the craving.
I conclude that my remote forebears evolved in an environment of brackish water.
If we're so smart…
“Why are humans the smartest animals on Earth?” you ask (24 March, p 3). Suppose any animal, in less than 2 million years, changed its environment so thoroughly that not only did many other species die out, but the existence of the animal itself was endangered. Would we call that animal “the smartest on Earth”? Maybe what separates us from other animals is that we are too “smart” to see our own mistakes for what they are.
Wilful genes
Your special report on God mentioned the human tendency to describe events in terms of agents, even when we know this is not truly the case (17 March, p 38). I have often thought that this tendency causes problems for people struggling to understand how evolution works.
We talk of antelopes evolving longer legs to escape from lions, of coloration evolving for camouflage, of evolutionary strategies and arms races, not to mention selfish genes. It is as if the antelopes deliberately set out to evolve longer legs; and it is not surprising that some people, realising that no creature actually sits down to figure out an evolutionary strategy, think evolution is nonsense.
Multiple morals
Robert Kurzban suggests we have at least two parallel systems for deciding right and wrong: one based on kin selection and one prohibiting specific actions (18 February, p 10).
These moral systems often suggest outcomes that are in conflict. I don’t doubt that we have a utilitarian mode, but we are also concerned with ensuring justice for the individual.
For example, killing an individual might benefit the public good by harvesting their organs, so it would be right from a utilitarian point of view, but could be wrong because it is unjust for the individual. I suggest that we have evolved instincts to consider the consequences of acting in accordance with both of these ethical systems.
Being social animals, we also have an instinct for complying with socially sanctioned arbitrary rules, giving the potential for a three-way split.
For example, working on a Sunday should be allowed for the general public good; to protect the shop worker there is a legal provision in the UK to opt out; and the Bible requires Sunday workers to be put to death (). Fortunately, that third option is not currently promoted.
No evidence
Charles Darwin suggested humans first stood up to free their hands to use tools. Kate Douglas says we know this “cannot be right since the oldest tools are a mere 2.6 million years old” whereas bipedalism arose 4.2 million years ago (24 March, p 36).
Who can be certain there are no older relevant stone tool finds to be made? And what of other materials? Many areas have no stone and certainly no flint. We may have stood up to more easily jab animals with poisoned sticks that were sharpened on rocks; preservation of such tools would be very unlikely.
From Elaine Morgan
Wading in water is the only known circumstance guaranteed to induce apes of all species to walk on two legs, even though in their case the process is still slow, clumsy and unstable.
It is odd, then, that in considering why we lost our fur, Douglas’s main charge against the aquatic theory was that it “lacks fossil evidence to back it up” (24 March, p 39). That surely applies in equal measure to all the “why” theories.
Even odder is the objection that a waterside habitat would have rendered us more “round and lardy”. Indeed it would, and did. We have 10 times as many fat cells as do chimpanzees.
Mountain Ash, Glamorgan, UK
From Brian Horton
Douglas suggests that because pubic lice developed as a separate species (from gorilla lice) 3 to 4 million years ago, we probably lost our body hair about then. She also reports that body lice, which live in clothing, split from head lice only 72,000 years ago, plus or minus 42,000 years. This suggests humans did not wear clothes for about 3 million years after losing their hair.
But when humans first lost body hair they may have worn woven fig leaves – or other plants – which are an unsuitable environment for lice. Did head lice differentiate only when humans began wearing hats, offering a niche they could move into more readily? They could have moved when different clothing offered a suitable habitat.
West Launceston, Tasmania, Australia
How did we leap?
Your report on the biggest questions in human evolution (24 March, p 34) does not adequately address how the “great leap forward” occurred about 50,000 years ago. From that point on, humans were radically different from their ancestors and other creatures. We assume this had physical or biological causes, such as climate change or genetic mutation; yet our ancestors at that time would have been subject to the same biological and environmental influences as other large mammals.
So how did it come about? Whatever the causes, the change seems to have been unique, as if humans entered a new dimension of being. No other creature that we know of has made such a radical and relatively sudden departure from its predecessors.
Bodies of the future
Stem-cell research promises great changes to our lives by providing spare parts for our bodies, so extending human lifespan to centuries. Surely their effect on the human body 100,000 years hence will be just as profound as those arising from genetic engineering, climate change and so on, suggested in your Deep Future special (3 March, p 37).
Virtually first
You reported on animals made to think inside a virtual world (17 March, p 6). Virtual reality for animals is a concept I proposed nearly 20 years ago in a paper entitled “Cyberspace for animal husbandry” (). I suspect this is widespread in scholarship. Your idea is only recognised and taken up when the time is ripe.
The editor writes:
• Indeed, it seems that “major innovations occur not when an inventor is struck by a bolt from the blue, but when the scientific and social conditions are ripe” (18 February, p 3).
Ineffable deities
Victor Stenger betrayed a basic mistake in supposing that the methods of natural science could possibly test the existence of a supernatural being (17 March, p 46). There is no test: quite apart from the hubris, it is impossible. To put it very crudely, if God exists, he/she/it/they will not be that easily fooled.
There are answers to all Stenger’s other points – invalid inferences, questionable statistics and assumptions, and so on. Stephen Jay Gould was right: science has nothing special to say about God, angels or ghosts, and theology has nothing special to say about relativity, evolution or atoms.
Knowledge is a self-consistent whole, but it has different parts: we must use the methods proper to each part.
From Nigel Braithwaite
You state “Religious claims still wither under rational scrutiny and deserve no special place in public life” (17 March, p 3). So somehow it is “rational” to expect people to believe that a particle can be in two places at once and indeed not in either, and it is “rational” to base an entire branch of science on the existence of a particle which – as yet – cannot be seen, but it is not “rational” to believe in a deity (can be in more than one place at a time, cannot be seen).
Redditch, Worcestershire, UK
From Jason Johnston
The image of a bearded, divine figure in “The God hypothesis” shows Hebrew writing above the head (17 March, p 46).
It is evidently meant to be the Tetragrammaton, the four-character divine name YHWH, commonly read as Yahweh, but in this case it is reversed, so the image shows HWHY.
Perhaps the artist intended to represent a new and appropriate name: Who He?
Sydney, Australia
From Tom Weinberger
It reads Hooey, as in “a lot of…”
Jerusalem, Israel
The editor writes:
• Jason Johnston is right. The artist reversed the writing intentionally, to convey a sense of uncertainty appropriate to the article it illustrated.