Why eight cousins are better than one brother

Professor Debashish Chowdhury of IIT Kanpur has studied the way ants behave as they march out of their nest to gather food, and back carrying it to the nest. He found that they behaved in a perfectly disciplined way with no traffic jam along the routes. The outbound ones yield the right of way to the inward bound food-laden traffic.

The food carriers do so for the entire colony, not just for themselves. In doing such ‘public service’ they exert themselves and expend energy. With honey bees in the hive it is more striking. A worker bee toils for the whole colony, but all this does not help its own reproduction. Many such worker insects in the so called “eusocial insects” are sterile. Clearly this is no survival of the fittest. How and where does self-interest lose its importance in natural selection and in the origin and evolution of species?

Benefits propagation

All that Darwin said about this puzzle was that such helping each other in a family or colony benefits the whole group in propagating itself. Dr. William Hamilton elaborated this idea in the 1960s, and pointed out that cooperation helps the spread and propagation of genes down generations. After all, your relatives share some of your genes. If you help your relatives, and the more children they produce, the more these genes spread. The extended family line is stabilized and becomes a large family tree down successive generations.

John Maynard Smith called this kin selection and said “by kin selection, I mean the evolution of characteristics which favour the survival of close relatives of the affected individual, by processes which do not require any discontinuities in the population breading structure”. In simpler words “even if I die, my family would be saved and grow generation after generation.” J B S Haldane, the great British biologist who took on Indian citizenship and worked here, described this pithily: “Would I lay down my life to save my brother? No, but I would to save two brothers or eight cousins.” Why? Because his brother is 50 per cent identical to him by descent, and his cousins, 12.5 per cent. In losing one but saving two brothers he assures his genetic longevity, as he does by saving eight cousins. Here then is a cost-benefit calculation towards saving the genetic lineage. Starkly put, we are all simply carriers of genes which manipulate us for their survival and propagation. Richard Dawkins describes all living beings as gene machines in his startlingly titled book ‘The Selfish Gene.’

That kin selection operates even in organisms that have no ‘brains’ was shown by Dr. Susan Dudley of Canada. She compared the growth patterns of unrelated plants sharing a pot to plants from the same clone. While unrelated plants competed for soil nutrients by aggressive root growth, siblings did not.

Kin selection helps explains cooperation among family members, But we see helping hands between individuals who are genetically unrelated strangers.

The evolution

How did this evolve? Some say that we can expand the idea as group selection for people living in a close- knit community. This is easy to see in a group that lives together and inbreeds. The whole group is then genetically interrelated, however loosely if might be.

Others have extended this to occur between two or more communities, where interaction occurs — be it competition or comparison. They find that groups with greater cooperation among its members do better and wish to emulate them.

Among two competing tribes, “if one tribe included a greater number of courageous, sympathetic and faithful members who were always ready to warn each other of danger, to aid and defend each other, this tribe would succeed better and conquer the other” surmised Charles Darwin in ‘The Descent of Man.’

Evolutionary biologists are digging into the origin and instances of reciprocal altruism (which is pretty much on a one-to-one basis), kin selection, group selection and cooperation in “lower organisms” and those that came on earth long before we did. Elizabeth Pennisi cities, in her article ‘On the origin of cooperation’ in the September 4, 2009 issue of Science, instances where bacteria and even viruses exhibit cooperative behaviour.

She refers to the experiments of Dr. Stuart West with the microbe pseudomonas aeruginosa. This bacterium releases chemical signals which other fellow bacteria sense and, in turn release many useful chemicals including a film on which many can attach and aggregate as a group.

Major challenge

This phenomenon has been evocatively described as “quorum sensing.” A major challenge to microbiologists is to develop bio-film busters, disassemble the quorum and disable the pathogen.

One can go even “lower” and cite examples of viruses — simple gene collections wrapped in protein envelopes — that do not quite qualify as living (they have the reproduction software but not the metabolic hardware; they use the latter from the “host” they invade. You are alive only if you have both in yourself).

Viruses called phages choose bacteria as their target in which to multiply. Pennisi cites the work of Drs. Joel Sachs and James Bull, which took the dictum “in unity is strength” to its limit.

Two different phages were allowed to infect a bacterial strain, and monitored for many generations. After several generations, the two started packing their genomes into a single protein envelope. One of the phages eventually lost the genes needed to make it own protein coat; as long as we are infecting the same cell, why not join in doing it? The ultimate in cooperation!

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Printable version | Nov 23, 2021 9:15:26 PM |

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