Ancient hybrids
I can’t deny James McCartney’s point that the caterpillar and the butterfly are products of the same genome (6 March, p 32). I do contend, however, that this genome resulted from the fusion of two genomes when two distantly related animals hybridised.
A caterpillar-like animal (an onychophoran) hybridised with an ancestor of modern butterflies to give the first lepidopteran with a caterpillar larva. Metamorphosis thus represents a change in taxon during development. The drastic changes that take place in the lepidopteran pupa give an indication of the degree of difference between an onychophoran and a lepidopteran.
Hybridisation with onychophorans also gave caterpillar larvae to scorpion flies (Mecoptera) and to sawflies (Hymenoptera).
The forms of insect larvae are not well correlated with the forms of adult insects. The basic forms of all larvae were transferred from foreign taxa, and in most cases the donor group can be identified. The occurrence of caterpillar larvae is one of dozens of examples explained by the theory of larval transfer. The theory and its implications are the subject of my recent book, The Origins of Larvae (Kluwer).
Jupiter's influence
While the work of Mausumi Dikpati suggests that meridional flows in the sun’s convective layer may allow us to forecast sunspot activity (6 March, p 38), other forces may also be at work. In particular, the giant planets in the solar system may play a role through the gravitational pull they exert on the massive amount of fluid flowing in the outer layer of the sun.
Curiously, this gravitational force can be expressed as a Fourier series whose most important terms have interesting periodicities: one of these coincides with the 11-year cycle of the sunspots. What we may be seeing, therefore, is the direct influence of planetary tidal forces and their effects on the stability of the magnetic loops created in the meridional flows in the sun’s convective layer. These forces could be a major factor in the cycle of magnetic loops believed to create the sunspots.
Jupiter is the largest contributor to the solar plasma tides. It may eventually transpire that its influence contributes to our climate.
Saving cuddly species
One of the often-used arguments in support of ecotourism is the cash it brings in to support wildlife conservation programmes (6 March, p 6). The flaw in this view is that these programmes often appear to be speciesist in the extreme, aimed at conserving large, cuddly or exotic species of mammal in order to attract ever more tourists.
A conservation initiative to save an endangered “creepy-crawly” insect that few 鈥� other than the scientists 鈥� have ever heard of is unlikely to be as successful in bringing in big-spending visitors. Most people just want to see tigers, leopards or cheetahs. Any international agreements that emerge to accredit and regulate ecotourism and its impacts must address this issue, otherwise we will end up with market-driven conservation programmes that will put biodiversity at risk.
Bionics tomorrow
As a below-elbow amputee and a journalist who relies on the use of a prosthesis for everyday living, I was most interested in your article on “rebuilding” limbs (28 February, p 26).
However, from practical experience I think that the title might well have read: “We can rebuild them鈥t a price”. Very few prosthetics users have access to the large sums required to purchase existing state-of-the-art artificial limbs.
Another big problem would be the interfacing of the body to the prosthesis. Osseo-integration (living bone to prosthetic coupling) is in its infancy and is not suitable for everyone. The problems for the upper extremity amputee are complex.
Unfortunately, as usual when I read articles and reports on the same subject, I think it’s a continuing case of “bionics tomorrow” for the majority of artificial limb users.
Dream on
Though I read Peter Bentley’s article on “perfect software”, with interest, I feel I must inject a little realism (6 March, p 28).
Computer programming is unfortunately subject to periodic fads. Each fad begins by being hailed as a new paradigm that could make most programmers redundant. For example, neural networks were supposed to allow the computer to learn like the human brain. Future computers would not require programming, merely a bit of teaching 鈥� usually with a list of example inputs and the desired response. Following that, as Bentley acknowledges, the idea of genetic programming was touted as the next great step forward before its limitations were encountered. Each fad, so far at least, ends up all but forgotten.
It is all too easy to hype up new methods, and underestimate more conventional modern software and the people who produce it. Most commercial software is enormously complex 鈥� indeed it is one of the marvels of the age. If the guts of software were visible as it operated, like the parts of a machine, the intellectual effort that created it might be better appreciated.
When Bentley has grown a commercially viable piece of software 鈥� a word processor, say 鈥� I will be much more impressed.
Letter
Bentley says: “Unlike computer software, nature’s code is not full of bugs.” On the contrary, nature’s code has all too many bugs. Organisms suffer from genetic and embryological defects, sometimes crippling and sometimes lethal. Even when developmentally perfect, organisms eventually crash (or in other words, die) within a finite time. Nature does not produce perfection; it produces systems that work long enough to do something useful before they crash. Which is what, de facto, designed software does.
Humans can write software that conforms exactly to its specification. It is not easy and it is not cheap, which is why it is often not done. But it can be done. A major software manufacturer recently stopped having two teams implement the same specification 鈥� to create systems with different bugs that would not crash at the same time 鈥� in favour of having twice as many eyes scrutinising the specification for errors.
As with human-written software, evolutionary software cannot develop defences against problems to which it is never exposed. The virtue of evolutionary programming is that it puts the major emphasis on testing, traditionally the poor relation of programming. In this, it is to be admired. However, modern software development techniques such as extreme programming also emphasise testing early and often, and to good effect. The problem is not actually technical, but rather one of management and marketing.
Plague of salt
Your item about plans to send water southwards from Siberia to central Asia speculated about the climatic effects of changing the flow of water to the Arctic (7 February, p 8). Consideration should also be given to the climatic effects of doing nothing, and risking further shrinkage of the Aral Sea.
It is believed that in the period AD 200 to 600 the Aral and the Caspian seas both shrank considerably. This period of drought on the steppes saw great distress in western Europe as the previously benign climate deteriorated dramatically. Perhaps some unknown factor was at work, but we can already see great quantities of salt, deposited from the Aral Sea, being blown into the air during storms. The millions of tonnes of salt could act as condensation nuclei and have a major impact on world climate by increasing cloudiness over a wide area.
Filthy frescoes
Of course, works of art 鈥� like people 鈥� can age gracefully, and wrinkles on an old face can be very expressive. But dirt is a different matter (21 February, p 30), and it was the soot of centuries that had dulled the frescoes of the Sistine Chapel.
When I saw them about 30 years ago I was saddened to see only dull hues. Now I can admire the restored frescoes with their original colours and shades. I am convinced that Michelangelo, had he seen the state the frescoes were in, would have done whatever he could to clean them and give them back the aspect he created.
It is true that in some cases, restoration may destroy the charm of old artefacts. Removing the verdigris from baroque domes to reveal the original reddish copper beneath would make me uneasy. But it would be wrong to condemn all restoration solely on the basis that decline is natural.
Don't scratch
Your article on diffraction gratings as a method for colouring materials is interesting (28 February, p 24), but I have to question its practicality. Mool Gupta reportedly suggests that the ability to embed colour into a material would eliminate the need for “expensive” painting.
What the article fails to mention is that any material which gets scratched would lose its colour just as a painted object would. What’s more, you would not be able to correct the problem by slapping on a coat of paint. Instead, you would have to replace the entire surface 鈥� a far costlier proposition.
Black hole in B flat
I missed the deadline at the end of last year for Feedback’s contest inviting suggestions for new scientific terms. But The Word item on space music has inspired this belated submission (28 February, p 49).
For very low frequencies like those making noise in space we need the terms “millihertz” (once every 1000 seconds), “microhertz” (once every million seconds), and so on. For example, the Earth rotates on its axis with a frequency of approximately 69.5 microhertz.
As for the sound emanating from the black hole mentioned in your article, it has a frequency of about 3.17 femtohertz. My calculations confirm the astronomers’ claim that this is a very low B flat.
Mirror image
Apparently, it is possible to get a plasma TV screen for 拢2500 that can also be a mirror, with a function to let you watch a programme while combing your hair (28 February, p 22). It is worth pointing out that there is a cheaper option. Position an ordinary mirror opposite an ordinary TV and you will be able to see the TV while looking in the mirror. This also has the additional advantage of making otherwise predictable repeats look completely different.
For the record
鈥� Due to an editing error in last week’s Biobusiness Trends feature (13 March, p 52), we stated that the biotech company Celltech was worth 拢1.1 million (about $2 billion) 鈥� the true figure is 拢1.1 billion (about $2 billion).