Ancient islanders
Arsenic-loving fern
Wilderness warning
Design from Nature

Ancient islanders

There have been reports of extraordinary life spans in some individuals, notably in Vilcabamba in Uruguay and in Georgia in the area lying between the Caspian and Black Seas. In Science for March 16, Robert Koenig describes the strange affair of the inhabitants of the island of Sardinia where, it is believed, a larger proportion of men than anywhere else in the world survive to 100-plus.

In the village of Tiana in the Sardinian mountains Antonio Todde celebrated his 112th birthday on January 22 this year. Antonio is a shepherd living high in the mountains, where he has welcomed hundreds of pilgrims wishing to congratulate him on his extraordinary longevity. Similar phenomena reported from the Caucasus, the Andes, western China and the Japanese island of Okinawa have been doubted, since no proof of date of birth has been available, but in the Sardinian instance there seems little reason to doubt the years claimed. Age in Roman Catholic countries has always proved more reliable than elsewhere, since certificates of baptism have been available for many generations and guesswork is ruled out.

In most countries where reliable data are available, five women reach their century for every man who does so. But researchers at the University of Sassari have found that in Sardinia the female–male ratio is only about two to one, and that in its mountains there are roughly equal numbers of men and women centenarians. The isolation of villages there provides an area of genetic restriction where research can be carried out.

It is estimated that there are some 100,000 centenarians world-wide, and that the numbers are increasing. Currently the oldest person known is a French woman aged 114 years. In Sardinia more than 50 instances have been verified beyond doubt, where the age of 100 has been exceeded.

Mortality after the age of 80 is relatively low, and several reasons have been suggested to account for this. A healthy agrarian lifestyle with low stress levels has been claimed, but some of the aged men, despite otherwise low-stress outdoor habits, have at some time been heavy smokers and have participated in warfare.

There also may be a genetic factor to consider. For example, two Sardinian brothers, Pietro and Antonio Brundu, have reached the ages of 103 and 101, respectively, despite marked differences in their general health.

Inbreeding, although generally considered unhealthy, may enable the Sardinians to live longer. In the remote mountain villages most residents are descendants of only a few families who originally settled there, and genetic diversity is accordingly only slight. In some individuals the immune system may play a major role in determining longevity. The immune response centred on T- and B-lymphocytes tends to deteriorate with age, although general immunity dependent on macrophages may improve. These changes occur between 60 and 70 years. More frivolous critics suggest that the local red wine is a life preserver.

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Arsenic-loving fern

A report from Florida in Nature for February 1 describes a fern native to that state which is extremely efficient at extracting arsenic from soils and concentrating it in its above ground structures. The American brake fern, Pteris vittata, is claimed to be the first found to function as an arsenic hyperaccumulator. It was discovered on a site in Central Florida that was heavily contaminated with chromated copper arsenate. Plants at the site were tested by atomic absorption spectroscopy, but of 14 species investigated only the fronds of Pteris vittata contained large amounts of arsenic (3,280 to 4,980 ppm). Plants from an uncontaminated soil site (0.47 to 7.56 ppm arsenic) contained 11.8 to 64 ppm, and others from an adjacent site (18.8 to 1,603 ppm) contained 1,442 to 7,526 ppm.

It is evident that, apart from being able to thrive in soils containing up to 1,500ppm of arsenic, brake fern can accumulate large quantities of the metal rapidly in its fronds. Concentrations in the roots were much lower. Addition of 100ppm arsenic to growing ferns stimulated them with an increase of 40 per cent biomass. Almost all the element present was in relatively toxic inorganic compounds with little organoarsenic. There was evidence that during translocation from roots to fronds pentavalent arsenic was converted to trivalent forms.

Since the fern is versatile and hardy, preferring sunny and alkaline environments, easy to propagate and perennial, it is believed to hold great potential for the low-cost recovery of arsenic-contaminated soils.

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Wilderness warning

The ecologist sees the decline of the great natural buffer of wilderness as an element in our danger. Wilderness is not remote or indifferent, but an active agent in maintaining a habitable world, though the co-operation is unconscious.
— Frank Fraser Darling: 'Wilderness and plenty' (Reith lecture 1969).

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Design from Nature

The ancient Egyptians developed a fascinating concept in their design of pyramids and sphinxes, both shapes that ensure stability in the face of winds. Pyramids, it is true, represent a method of building where successive layers achieve stability by being staggered, and were also adopted by ancient cultures in the New World. Sphinxes are a different matter, and although they may reproduce the features of a large feline, they are intriguing from another angle.

In a paper published in Archaeology for March/April, a Boston University geologist, Farouk El-Baz, offers a convincing explanation of these Egyptian shapes. It is believed that the abrupt rise of Egypt's civilisation some five millennia ago resulted from the fusion of farmers working on the banks of the Nile with desert nomads who sought the valley on account of increasingly dry conditions. The incomers from the western desert were closely acquainted with the arid landscapes carved out by winds and sandstorms. They may have provided the background to the Egyptian passion for pyramids and sphinxes.

Solid rock masses in deserts undergo sculpture by the fierce winds into pyramidal shapes, which best resist erosion. The wind, aided by sand particles that it whips up, also carves the desert bluffs known as yardangs into masses resembling an upturned boat, with a profusion which always faces the prevailing wind and which becomes head-like. The process is attributed to the formation of vortices created by the wind as it scours the base of the rock mass and rises into the hollows thus produced. It seems reasonable to conclude that the Egyptians, far from inventing their architectural shapes ab initio, were inspired by the natural phenomena they observed.