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Neanderthals probably cooked their food before eating but would have struggled to eat root vegetables, according to a new study.

Geneticists have analysed ancient DNA from the remains of Neanderthals and another ancient human relative, the Denisovans.

They found that these prehistoric human ancestors lacked key genes needed to chew hard foods - just like modern humans alive today.

Neanderthals, depicted above by actor Ron Perlman in the film Quest for Fire, lacked genes that are thought to be essential for chewing tough raw food and so may have softened their food by cooking it over a fire 

Chimpanzees, our closest living primate relative, still have these mastication genes as they need to chew tough, raw food.

The scientists also found that Neanderthals and their Denisovan cousins may have struggled to digest starchy foods like root vegetables.

NEANDERTHAL BOIL IN THE BAG 

Neanderthals may have cooked stews in the skins of animals, according to some anthropologists.

Animal bones found at sites known to have been inhabited by Neanderthals are 90 per cent free of gnaw marks.

This suggests that fat and meat had instead been cooked off the bones.

A study of tooth plaque from the teeth of fossilised Neanderthal remains also suggest that they may have heated grains of barley.

However, there is no evidence that Neanderthals had any pots or pans to cook with.

Instead Professor John Speth, an archaeologist at the University of Michigan, believes that they used animal paunches and folded bark to make bags that they could boil their good in. 

A study of plaque found on Neanderthal teeth like the one above suggests they ate grains like barley

This is because, like chimpanzees, they had few copies of genes that release enzymes into the saliva and start digesting the starch as it is being chewed.

Modern humans have around six copies of these saliva digesting genes while Neanderthals had just two.

Neanderthals may also have tasted food in a different way from the way we do today and perhaps enjoyed plants that we find unpalatable.

The researchers discovered that they had a completely unique variation in genes responsible for tasting particularly bitter compounds.

They also lack two other taste receptors found in chimpanzees for tasting bitter foods.

The findings raise tantalising questions about whether differences in the diet of Neanderthals compared to modern humans lead to them dying out.

Their lack of digestive enzymes in their saliva would have meant they struggled to extract as much energy from starchy tubers compared to their Homo sapien counterparts.

Changes in the vegetation around them could have also meant some of their preferred foods disappeared. 

While Neanderthals, who lived between 280,000 to 40,000 years ago, are known to have mastered control of fire, little is known about the food they ate.

Analysis of their fossilised teeth has provided some clues that they may have used the fire to cook their food.

Now the new study has provided further evidence that they did.

Cooking is seen as being a key innovation that guided the course of human evolution as it makes important nutrients and higher levels of fats more readily available to the body during digestion.

Professor George Perry, an anthropologist at the Pennsylvania State University, who led the research, said: 'A number of major dietary transitions have occurred during the 6 million years of hominin evolution, including substantial increases in the consumption of meat and starch, the cooking of food, and the domestication of plants and animals.

'We hypothesize that the functional loss of a gene that otherwise encodes an important masticatory muscle protein may very well have followed hominin control of fire and the advent of consistent cooking behavior, which results in substantial food softening and reduces demand on the masticatory apparatus.'

Professor Perry, along with colleagues at Cornell University and the University of Texas, analysed the published genome sequences obtained from the fossilised remains of Neanderthals and Denisovans.

The Denisovans are thought to have been a sister group to Neanderthals, splitting from a common ancestor around 60,000 years ago.

They are thought to have lived further east than the Neanderthals that spread through Europe and the two species are thought to have eventually died out around at around the same time.

Little is known about the diet and habits of Neanderthals, shown above in a museum model in Duesseldorf

Root vegetables like parsnips and turnips, above, contain a lot of starch that is a valuable source of energy but Neanderthals appear to have lacked important enzymes in their saliva needed to help digest these tubers

The study found that like their modern human cousins, both these extinct hominins lacked the MYH16 protein, which is linked to large powerful jaws.

Unlike modern man, however, they lacked the genes needed for digesting the lactose in cows' milk. This is thought to have evolved with the advent of agriculture some time later.

The two ancient hominins also lacked genes used for tasting bitter food in chimpanzees - TAS2R62 and TAS2R64.

However, the Neanderthals had a unique version of another bitter taste gene called TAS2R38.

This gene is known to be essential for tasting the bitter flavour of a chemical called phenylthiocarbamide (PTC) and other related chemicals.

The fruit of the Chinese-laurel tree, Antidesma bunius, is known to contain chemicals similar to PTC that can only be tasted by people with this gene.

Around 70 per cent of people can taste PTC, but this varies according to population - 42 per cent of Australian Aborigines and Papuans from New Guinea cannot taste it.

The scientists analysed the genome sequences obtained by extracing scraps of DNA from the fossilised remains of Neanderthals, like this skull from an adult female , on display in the Natural History Museum

The new findings, which are published in the Journal of Human Evolution, suggest that while Neanderthals may have been able to taste this bitter flavour, it may have allowed them to only taste a specific sub-group of these chemicals. 

This would mean they perhaps would have avoided certain types of foods due to their bitter taste.

The Neanderthals and Denisovans also had just two copies of an amylase gene, used to digest starch from root vegetables in the salavia, far fewer than in modern humans.

Some experts have suggested that Neanderthals ate large qualtities of root vegetables as a rich source of energy in their hunter-gatherer lifestyle.

However, Professor Perry said: 'We can only conclude that if early hominins were consuming large quantities of starchy foods, as hypothesized, then they were likely doing so without the digestive benefits of increased salivary amylase production.'

Professor Perry and his colleagues added that it may eventually be possible to unravel exactly what foods would have tasted like to Neanderthals and what flavours they enjoyed by examining the receptors involved in smell.

They said: 'The timing of olfactory receptor gene gains and losses and functional changes could provide insights into hominin dietary evolution and evolutionary ecology. 

'This analysis is currently challenged by our limited understanding of the specific functional consequences of olfactory receptor variation and by the short sequence reads typically obtained from ancient DNA, which often cannot be mapped uniquely to specific, highly similar olfactory receptor genes. We are hopeful for progress on all of these fronts.'