11/29/2006
Forward and Backward
Last Friday’s Star-Ledger noted the death, at age 111, of Ernest Pusey, one of the very few remaining veterans of World War I. Less than two weeks before he died in Florida, Governor Jeb Bush had presented Pusey with a World War I Victory Medal. Am I related to Mr. Pusey? My mother’s maiden name was Pusey. She was born just a couple of years after Ernest. Not only was her father’s name Pusey but her mother’s maiden name was also Pusey. My grandparents were cousins. Apparently, marrying a cousin was not that uncommon back in the 1800s.
Today, the dangers of marrying within a family are well known. If there’s a defective gene in the family and both parents carry the gene, it’s likely their children will also inherit that gene. If only one parent carries the culprit gene, this possibility is vastly reduced or eliminated. The “good” gene from the other parent supplies the “good” protein that prevents any associated disease or deformity. My mother was one of four sisters. All four died at age 69 and I’ve often wondered whether there was a “bad” gene shared by their closely related parents, my grandparents.
Some time ago, I read about a family in which some siblings walked on all fours. There was a claim that this was “reverse evolution” in which an ancient gene was activated taking the siblings back millions of years ago when our ancestors walked on all four limbs. Last week I watched PBS’s Nova program about this family, which lives in a remote section of Turkey. Sure enough, the father and mother are close cousins. They had 19 children, 12 of whom are perfectly normal.
Six children, however, walked on all fours; five are still living, ranging in age from 18 to 34. A seventh sibling walks on two legs but has a very unsteady gait resembling that of a drunken man. The program was disturbing; one look into the eyes of these unusual individuals and you knew that they suffer from more than their strange mode of locomotion. They walk on the palms of their hands, not a throwback to our early ancestors.
Three million years ago, our human ancestors walked on two feet but also maintained a wrist bone structure found in our primate cousins such as the chimpanzee. Our great ape relatives can walk on their two feet or on all fours. In the latter case, they walk on their knuckles. The wrists of apes and our 3-million- year-old ancestors such as Lucy, mentioned here recently, are and were not flexible. Our wrists, on the other hand, are quite flexible and permit the Turkish siblings to walk on their palms, an argument against the “reverse” evolution claim.
Indeed, one British researcher, Nicholas Humphrey, says that calling the siblings a case of backward evolution is insulting to the family and scientifically irresponsible. In the remote village, neighbors tend to shun the family and children taunt the five siblings. Apparently, the family’s Islamic faith and the remoteness of their village have heretofore led the family to accept their fate without attempting to seek help. With the public exposure, however, things have changed.
The family has allowed MRI brain scans and analyses of blood samples to find the defective genes. The brain scans reveal a big problem – the sibling’s cerebellums are significantly smaller and deformed compared to those of normal individuals. The cerebellum is involved in balance and coordination of limb movement. The affected siblings also have difficulties with language. Studies are still in progress to pin down the exact gene or genes responsible for the strange behavior.
Remarkably, it seems that the father and mother, accepting their fate, did not or could not seek out expert medical attention. Nobody had thought to try to correct the four-limb problem by even having the siblings try using a simple walker. Now, however, a Turkish doctor expert in physical rehabilitation has the siblings working with walkers and parallel bars to try to achieve a bipedal mode of walking. The doctor held out hope that the four sisters would eventually walk more or less normally but did not expect the brother, who has been walking this way for 28 years, to ever be able to switch. However, the most touching part of the Nova program came near the end when the brother appeared walking, albeit very shakily, upright on two feet.
Normally, a baby who showed no signs of walking on two feet would be referred for medical attention and physical therapy and would soon be walking on two feet. The idea of reverse evolution would not arise. It may not qualify as evolution but the Nova program briefly showed a dog in Oklahoma City named Faith. Faith was born without her two front legs. Yet she walks around the city as upright as you please on her two hind feet. I should have her posture!
Now let’s consider a case of “forward” evolution that in a sense is a case of reversing an evolutionary trend in order to promote survival. Brian Trumbore called my attention to an article by Lewis Smith in the November 17 New York Times. The Times article dealt with work by Jonathon Losos and coworkers published in Science on the same date. Without Brian’s alert, I would have ignored the Science article, titled “Rapid Temporal Reversal in Predator-Driven Natural Selection”. The research, on lizards, offered the researchers from Washington University in St. Louis and the University of California, Davis a chance to spend two Mays and a November in the Bahamas – not bad.
This tale involves the brown arole lizard, which spends roughly 40% of its time on the ground and the rest up in trees. Over time, the brown lizard has developed long legs that allow it to run faster to get away from predators. The northern curly-tailed lizard is the bad guy; Curly tends to eat Brownie. However, Curly sticks to the ground. In the Bahamas there are lots of small islands and on some of them only the brown lizards are present. So, what would you do if you were Brownie and someone dumped a bunch of the curly-tails on your island? Well, I don’t know about you but I would take to the trees pretty quickly since Curly sticks to the ground.
The researchers found 12 small islands in the Bahamas that only had the Brownies on them. On six of the islands they introduced substantial numbers of the curly-tails, leaving the other six islands untouched as controls. At the beginning and then at six- month intervals they made a careful census of the brownies, measuring them and noting their locations. As I would have done, the Brownies started climbing and after 6 months spent roughly 10% of the time on the ground, not the normal 40%. After a year, the time on the ground was down to nearly 5%.
In the first six months the Brownies fared better with longer legs, allowing them to run faster to avoid the Curlies when first introduced. However, in the next six months, as the Brownies took to the trees, it became more advantageous to develop shorter hind legs to better navigate on the tree limbs and branches. In other Caribbean islands, it has already been shown that, when the lizards spend more time in the trees, their hind legs get shorter. Hence the “reverse” evolution in this case where introducing a predator, spurred a rapid change in habitat and a reversal of an existing trend to develop longer legs. Evolution can happen quickly and not just in the world of drug resistant bacteria and viruses.
Incidentally, my 79th birthday is coming up in a few weeks. Does that mean I owe those extra ten years to my father’s good genes? He lived into his 90s. I’ll never know.
Allen F. Bortrum
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