How does a new variety of bacteria come about? Imagine a small change occurring by chance in its genes, which allows it to withstand a stress, say a life- threatening drug or an antibiotic. Since bacteria multiply fast in minutes and hours, we find the drug resistant variety take over, establishing themselves over the drug sensitive ones in a few weeks.
What is true for bacteria is true for plants and animals except the time frame here is in years, decades, centuries or millennia, since the generation times are longer. And when they are stressed — say by climate or environment change, or domestication leading to local changes — they too produce new varieties or hybrids.
Do such stresses produce mutations one after another (incrementally) or does the genome respond in a more wholesale manner (jerky or punctuated)? Biologist who believe in incrementalism criticize the ones who subscribe to the latter as “Jerks” while the punctuators return the compliment by calling their opponents as “Creeps”.
Take a plant like maize, wheat, cotton or rice. It experiences episodic changes such as large changes in climate (as happened on earth in an archaic period) or when man imposed newer environments on it upon domestication.
How does the plant respond to such stresses? Will it adapt over centuries, based on incremental changes in its gene, and one after another, hopefully each mutation helping the earlier one? Or can a larger scale change (jerkier rather than creepy) occur and generate never varieties and hybrids?
The biologist Dr. Barbara McLintock was studying how genetic changes occur in maize (corn). And over years of laborious study, she found to her surprise that wholesale shifting of gene sequences occur within the genome.
DNA sequences within the genome move about, cutting and pasting, or copying and pasting themselves. The genome is thus a mosaic, whose sequences and hence messages can change, yielding new varieties. (As an example, here is a sentence: “She, Voltaire said, is a nice person”.
Now cut and paste, or copy and paste words, and you get: “She said Voltaire is a nice person”; or “She said Voltaire said she is a nice person”). She called these moving DNA sequences as transposable elements of transposons. For this novel discovery, she received the Nobel in 1983.
Transposons or jumping gene sequences thus offer a mechanism for evolution under stress or upon domestication. This point has been underscored recently by a study of the cotton plant by a group at the University of Warwick in UK.
They took archaeological samples of cotton (two kind from Peru, one from Brazil and the fourth from Egypt) and analyzed their DNA sequences to find that considerable genomic reorganization occurs in domesticated plant while its undomesticated cousin maintained its genome sequence stably.
Domestication and its stress force the plant to use gene-jumping using transposons.
Cotton has not only experienced such episodic changes due to cultural practices of humans. It too, on its part, has made episodic changes in human behaviour and civilization.
This hoary plant was first domesticated in 6000 BC in the Indus valley. It spread from there to Africa and Arabia, where if begat the name Al Qutun (the Spanish changed if to Algodon and the English to cotton).
Independently, another variety of it was grown in Mexico, as early as 3000 BC. The early Asians and Mexicans spun and wore it and wore it. Along with spices, gold and silver, cotton too was a treasure of the ancient world that had to be looted by the colonials.
It is this looting and commercialization of cotton that promoted the ignominious and unpardonable history of slavery. Even as the Europeans discovered America, and converted much of its southern states into cotton farms, they needed labourers.
And between 1700 and 1900 alone, as many as 4 million Africans were enslaved and exported to the U.S. to be owned, bought and sold, just as animals, to work in cotton farms. (Even the founding fathers of America owned and used Negro slaves).
The result was booming business in cotton. By mid-1800s America was exporting nearly two billion tons of cotton per year.
True, there were murmurs against this inhuman practice, but when it exploded into a Civil War, President Lincoln intervened, won the war and unified the country.
But it was left to the heroism of the blacks (and their white supporters) led by the Gandhian Martin Luther King, who had a dream that ‘we shall overcome, we shall all be free some day' that led to equal rights for blacks and whites.
In India, one of the major finds of the East India Company (the boxwallas) was calico. This was a cloth made in Kozhikode (Calicut, hence calico) using both the fibre and the skin of the seed.
The company, and the empire that followed, made millions of Pounds yearly, thanks to Indian (and Egyptian) cotton. And when cotton mills were established in England during the Industrial revolution, cotton fabric became thinner, finer and more desired. Indian cotton cloth lost its value both in U.K. (where it was banned) and at home as well.
Gandhiji understood both the cultural and exploitative value of mill-made cotton; hence his spinning wheel and homespun khadi. Economic value apart, the sense of national pride and patriotism it brought about lasts even today.
Cotton thus brought about not an incremental or creepy change, but jerked an episodic, punctuated and profound change in Indian's spirit of nationalism.
How unjust, though, that in the era of current day khadi-clad netas, over a quarter million farmers killed themselves because they could not repay the loans they took to buy and grow cotton, and no relief is in sight.
dbala@lvpei.org
