By Judith Burns
Science reporter, BBC News
The remains from El Sidron were excavated under sterile conditions
DNA analysis of ancient remains shows that Neanderthals shared with modern humans the gene that gives the ability to taste bitter flavours.
Most people find the chemical, known as PTC, very bitter, but 25% cannot taste it at all.
The two groups have different taste receptors on their tongues.
Analysis of the 48,000 year-old bone shows that the genetic 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 the divergence of the lineages 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 recessive variant of the gene results in a functional change to the amino acids so that the protein is different and cannot bind to the bitter substance.
Both variants of the gene must have existed in Neanderthal populations
Writing in Biology Letters, the researchers describe how they amplified 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 excavated from this site since 2000.
Scientists are confident the sample was not contaminated with any modern human DNA as the remains were excavated under sterile conditions and immediately frozen.
The presence of the gene means that this particular Neanderthal individual could taste bitter flavours.
But researchers also determined 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 sprouts and broccoli and in some poisonous plants.
The ability to taste the chemical would help individuals avoid eating large quantities of toxic plants.
But the researchers say the fact that the recessive 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.