August 12, 2009

Neanderthals, Modern Humans Shared Tasting Gene

Scientists say that DNA analysis of ancient remains suggests that Neanderthals and modern humans shared the gene that give us the ability to taste bitter flavors, BBC News reported

A chemical called PTC is considered very bitter to most people, but 25 percent cannot taste it at all, because certain people have different taste receptors on their tongues.

But the genetic variation responsible for this difference also existed in Neanderthals, according to recent analysis of a 48,000 year-old bone.

"This means that this genetic variation predates the divergence of the lineages leading to Neanderthals and modern humans," said lead author Dr. Carles Lalueza-Fox from the Institut de Biologia Evolutiva in Barcelona.

Lalueza-Fox told BBC News that the non-taster is not something that occurs just in modern populations, but has something that was present at least half a million years ago.

Humans can taste bitterness because of the gene TAS2R38, which encodes for a protein in the taste receptors on the tongue.

But a recessive variant of the gene causes a functional change to the amino acids in non-tasters, so that the protein is different and cannot bind to the bitter substance.

For the study, the researchers amplified and sequenced the TAS2R38 gene from a Neanderthal bone sample found at El Sidron in northern Spain -"“ where the remains of 11 Neanderthal individuals have been excavated since 2000.

Since the remains were excavated under sterile conditions and immediately frozen, scientists are confident the sample was not contaminated with any modern human DNA, they wrote in the journal Biology Letters.

Experts say this particular Neanderthal individual could taste bitter flavors, due to the presence of the gene. But they also determined that he carried the recessive gene that blocks this ability.

Therefore, the Neanderthal population must have contained some individuals who were unable to taste bitterness.

Forms of phenylthiocarbamide, or PTC, can be found in leafy vegetables like sprouts and broccoli and in some poisonous plants. The ability to taste the chemical would help individuals avoid eating large quantities of toxic plants.

However, researchers believe there must be some genetic advantage in not being able to taste bitter flavors since the recessive form of the gene has survived in modern humans.


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