'Taste test' for Neanderthal DNA 古穴居人有味觉DNA

DNA¹ analysis of ancient remains² shows that Neanderthals shared with modern humans the gene³ that gives the ability to taste bitter flavours.

古故居人遗物的DNA分析显示他们与现代人一样的基因，可以使他们有品尝苦味的能力。

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Both variants of the gene must have existed in Neanderthal populations

Most people find the chemical, known as PTC, very bitter, but 25% cannot taste it at all.

The two groups have different taste receptors（味觉感受器） on their tongues.

Analysis of the 48,000 year-old bone shows that the genetic⁶ variation responsible for this difference also existed in Neanderthals.

According to the lead author, Dr Carles Lalueza-Fox from the Institut de Biologia Evolutiva in Barcelona, this means that this genetic variation predates（在日期上早于） the divergence⁷（分歧） of the lineages（家系，血统） leading to Neanderthals and modern humans.

Dr Lalueza-Fox told BBC News: "The non-taster is not something that occurs just in modern populations. It is something that was present at least half a million years ago."

The gene TAS2R38 encodes for a protein in the taste receptors on the tongue which allows us to taste bitterness.

In people who are non-tasters, a recessive⁸ variant⁴ of the gene results in a functional⁹ change to the amino（氨基的） acids so that the protein is different and cannot bind¹⁰ to the bitter substance.

Writing in Biology Letters, the researchers describe how they amplified¹¹ and sequenced the TAS2R38 gene from a Neanderthal bone sample found at El Sidron in northern Spain.

The remains of 11 Neanderthal individuals have been excavated¹²（挖开，凿通） from this site since 2000.

Scientists are confident the sample was not contaminated with any modern human DNA as the remains were excavated under sterile¹³（不毛的，无菌的） conditions and immediately frozen.

The presence of the gene means that this particular Neanderthal individual could taste bitter flavours.

Recessive gene

But researchers also determined¹⁴ that he carried the recessive gene which blocks this ability.

This means that the Neanderthal population must have contained individuals unable to taste bitterness.

The chemical in question is phenylthiocarbamide, or PTC. Forms of it are found in leafy vegetables like sprouts¹⁵（秧） and broccoli¹⁶（绿菜花） and in some poisonous plants.

The ability to taste the chemical would help individuals avoid eating large quantities of toxic¹⁷ plants.

But the researchers say the fact that the recessive（逆行的，劣性的） form of the gene has survived in modern humans must mean that there is some genetic advantage in not being able to taste bitter flavours.