A study found that the microscopic African sleeping sickness parasites haven't had sex in over 10,000 years. A team of researchers analyzed the parasite's genome and they discovered that every single sleeping sickness parasite that has infected the human population in the last 10,000 years all came from a single individual through asexual cloning.
The parasite's scientific name is Trypanosoma brucei gambiense. Scientists theorized that given such inability to reproduce sexually, it should lead to the parasite's eventual demise. Maybe not in the near future but in about several thousand more years.
The African sleeping sickness parasite accounts to over 6,000 deaths annually in sub-Saharan Africa. Transmission among humans is caused by tsetse fly's bites. The parasite was first thought to have lived among wild animals; however, human transmission began when livestock farming started around 10,000 years ago.
A team of researchers from Glasgow University found that the parasite's minute differences in its genome suggest that the species was built from a single predecessor through asexual cloning. This asexual cloning carries some major consequences.
Lead author Willie Weir explained that the genetic blueprint of an organism is programmed in its DNA. This is packed inside the chromosomes.
"Most organisms have two copies of each chromosome and, through sexual reproduction, the DNA within the chromosomes can recombine randomly," said Weir.
The process creates genetic diversity. Natural selection then eliminates harmful mutations and combinations among the population. This process helps in the species' continuing existence. Unfortunately, there are some species that don't reproduce sexually.
According to evolutionary theory's forecast, these species will face demise in the long run and because the genes are not mixed with others, asexual cloning should leave a genetic signature in the species' DNA. The predication has been going around for nearly 20 years but the so-called signature remains elusive.
Senior study author Annette MacLeod added that due to the lack of sexual reproduction, the single-celled parasites' chromosomes collected the telling mutations of its survival by duplicating itself numerous times.
The African sleeping sickness parasite makes up for its nonsexual survival by copying and pasting DNA, transferring it from a single chromosome to the next. The findings suggest that this can only last for so long. As a consequence, it is predicted that the species will become extinct in the long run.
Photo: Ed Uthman | Flickr
