Science for presidents

Biomedicine and Molecular Biology

The molecular face of evolution

Reconstructing the natural history of a living organism is above all a question of time and resources, experts say. The use of molecular technologies not only complements the contribution from the fossil record but is increasingly replacing it and thereby reduces the margin of error to “practically zero”. The investigation of the malaria plasmodium is one of the best examples.

XAVIER PUJOL GEBELLÍ | JULY 30, 2010

Anopheles gambiae is one of the mosquitoes that transmits the malaria vector

All living organisms have a genetic makeup that in addition to providing information on a specimen also provides key clues about its relationship to other species, past and present. This makes it possible to reconstruct the lineage of a species and, therefore, to establish the interaction of each with a given environment and its evolution over time.

To the surprise of researchers, there is not just one single gene or a single set of genes that provide this type of information or open unexpected doors for emerging disciplines. There is, for instance, the case of the HomeoBox genes, which guide the development of an individual from head to tail and from left to right (basis of the discipline known as evo-devo), the study of pseudogenes or introns, DNA sequences that indicate the start of a gene.

But the area where new techniques developed from molecular biology and genetics are making their largest impact is in the knowledge of certain organisms with great influence on human health. The case of the malaria plasmodium, knowledge of which has taken a quantum leap in just three years, is probably the most unique of them all. The increasing knowledge of its evolution is providing key clues for the development of biotechnology solutions to combat a disease that causes a half-million deaths each year, mostly among children under five years of age, and which accounts for 500 million cases worldwide, according to the World Health Organization (WHO).

Of birds and apes

Being a parasite, the plasmodium wants to live in some degree of harmony with their host. Otherwise, the advantages they enjoy adapting to an organism that provides them with sustenance would be lost if the red line that separates life from death were crossed. For many species, such as birds or apes, including chimpanzees, gorillas and baboons, this balance is maintained to perfection. Malaria occurs, but it is not lethal. The same goes for many of the human infections, although symptoms manifested by the infection are usually more severe. However, there are an enormous number of fatalities. Can evolution explain why? Knowledge of the evotlution of the malaria plasmodium provides key clues for the control of the disease

The prevailing theory, and the most plausible, according to experts, has to do with a possible jump between species. “Birds, especially chickens, have lots of malaria,” said Francisco J. Ayala, a biochemist at the University of California Irvine and one of the most reputable Spanish researchers internationally. One possible explanation, the scientist said, is that the strain of Plasmodium falciparum, which causes malignant malaria, jumped from birds to humans with the introduction of agriculture in the Neolithic period. “With the spread of agriculture, jungles were deforested; pools of water arose where mosquito could place their larvae; humans turned from nomadic life and established settlements; and there was a sufficient density for the mosquito to be able to complete its full cycle,” he said.

Comparing genomes enabled researchers to establish the degree of the evolutionary relationship between Plasmodium falciparum and Plasmodium gallinaceum, the guilty party for malaria in chickens. The same has also been done with the parasite that causes the disease in the great apes, Plasmodium reichenowi.

In the latter case, Ayala said, the establishment of the evolutionary line, in which Plasmodium falciparum would be “younger” plasmodia, is a recent discovery derived in large part on the development of DNA probes that can capture and amplify the genetic code sequences from the feces of gorillas and chimpanzees infected with the disease. The method is as reliable as blood tests and, of course, is far more accessible.

The biomedical route

The finding of the common ancestors for different species of plasmodium, besides allowing for a better understanding of the disease, is leading to “new and promising” preventive and therapeutic approaches, Ayala said. “The study of the evolution of the plasmodium provides us knowledge for the development of drugs against a disease that annuls almost an entire continent,” he said.

In this regard, Ayala believes that the arrival on the scene of Bill Gates and his wife Melinda “with million-dollar investments” is contributing decisively to change the face of a disease that before only attracted interest from industry and Western governments. For the Spanish scientist, a large part of the “industrial, commercial and intellectual underdevelopment” of Africa, where malaria affects 70% of its population (about 400 million people, according to WHO estimates), is attributable to the disease’s effects, with disabling high fevers and temperatures often exceeding 40 degrees Celsius.

AN INSULT TO SCIENCE AND RELIGION

Francisco Ayala is one of the leading experts in the study of evolution. His contributions, mostly on biochemical and genetic pathways, have earned him the honor of being named a member of the American Academy of Sciences and, for a time, president of the American Society for the Study of Evolution. It was in this role that he launched an unfinished crusade against creationism and its later derivative, Intelligent Design.
Ayala believes that both positions are virtually without any “support of intellectual depth” and that, at best, they come back to religion, albeit in an "blasphemous” way. “Attempting to tell the origin of life taking the Book of Genesis to the letter is nonsense,” he said. “And attributing the design of complex structures like an eye to some ‘higher architect or engineer’ is blasphemy”. For Ayala, it is enough to observe human nature to challenge the supporters of Intelligent Design: “Our jaw is badly designed, the same goes for the birth canal, through which the newborn's head cannot pass; and the female reproductive system is highly inefficient as attested to by the 20% of spontaneous abortions in the first two months of gestation. Any engineer would have been fired for much less”.

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