This week I am writing a piece on brain atrophy in relation to ageing. There has been quite a bit going on in the last couple of weeks in various fields of scientific enquiry. Before we move on to our key topic, one area that is positively bristling with excitement now is paleoanthropology. This is of course the study of ancient humans based on fossil evidence, tools, and other signs of human habitation.
The modern field of paleoanthropology began in the 19th century with the discovery of what we now know as ‘Neanderthal’ man. The first Neanderthal fossils were discovered in 1829 in Belgium and in 1848 in Gibraltar. They were not recognised as an early human species until 1856 when a much more complete specimen was discovered near Dusseldorf in Germany (known as ‘Neanderthal 1’).
Neanderthals and their typical morphological features are first demonstrated in fossil records dating back 400,000 years ago. Evidence of their existence then vanished 30,000 years ago. Well, what is interesting about that I hear you ask? If you are European or Asian about 1-2% of your DNA is Neanderthal DNA.
This is because modern humans overlapped with Neanderthal populations for a period and the obvious thing happened. As a result, many people living today have a small amount of genetic material from these distant ancestors.
Recently our understanding of the origin, distribution, and the evolution of early humans and their ancestors (such as Neanderthals) has advanced rapidly. Scientists have sequenced Neanderthal genomes from fossils discovered both in Europe and Asia. This genetic information is helping researchers learn more about these early humans. It is also useful as we can determine which areas of our genome we have in common with Neanderthals, and which areas are different.
This in turn will help researchers find out what differentiates modern humans from our closest extinct relatives. However, one of the things that puzzled scientists recently is that during morphological and genetic studies it appears that Neanderthals have a genetic contribution from an unknown mysterious group of non-European early ancestors. This may now be finally solved.
Some key pieces of this jigsaw puzzle and possible answers to this riddle have just been published in the scientific journal ‘Science’ on June 25th, 2021. A research team from Tel Aviv University have found the remains of a human that lived 120,000-140,000 years ago. They have called the new human species ‘Nesher Ramla Homo’ type (not particularly catchy but named after the place it was discovered!).
The remains represent a new species of human that appears to be an early ancestor of Neanderthals although genetic information on the samples has yet to be fully revealed. It transpires that this new species may have migrated from the Middle East through to Europe. Yet another ancient skull has also been recently studied in China that appears to be 146,000 years old. This was found in 1933 in the Harbin Province but only just recently attracted interest.
This has also been established as a new species called ‘Homo Longi’ (or ‘Dragon Man’). It is possible that this species could even replace Neanderthals as our nearest relative! Further studies are yet to be undertaken on Dragon man.
The Few Hunter Gatherer Societies Help us Reconstruct our Past
Another piece of valuable research that flew under the radar, this time in anthropology, was also recently published in the ‘Journals of Gerontology’ on May 26th (Gerontology is the study of ageing). One thing that is unbelievably valuable for anthropologists is to research and to reconstruct the physical activity and lifestyle patterns of our earlier ancestors. There are fortunately still a few hunter gatherer societies that exist.
They allow us to peer back in time to see how we once lived tens of thousands of years ago in a pre-industrial age. In June 2019 I wrote an article (‘How much exercise do we really need?’) based on the Hadza tribe who live on the fringes of the Ngorongoro Crater on the edge of the Great Rift Valley.
The research connected with them investigated how much time the Hadza spend engaged in moderate-to-vigorous physical activity (or MVPA). It then compared this with modern day lifestyles and detailed some intriguing results.
Our study from Journals of Gerontology meanwhile chose to study the Tsimane tribe in Bolivia. The Tsimane live a subsistence lifestyle of hunting, gathering, fishing, and farming. Roughly only 9,000 Tsimane live in the Beni department of the Bolivian Amazon, dispersed over 80 villages. Average village size is approximately only 100 individuals, but over half of all villages contain less than 50.
In the scientific community the Tsimane have status because they have the healthiest cardiovascular systems of any recorded population, which in turn increases their brains’ resilience to ageing and brain atrophy. This is according to the remarkable results just published in our study.
The Tsimane have the Healthiest Cardiovascular Systems Known to Science
A previous study published in 2017 in the Lancet found that the Tsimane had the lowest levels of coronary atherosclerosis ever recorded and now it appears that this also extends to brain atrophy. They are approximately five times less likely to develop heart disease due to a diet high in fibre, fish, lean meat and vegetables obtained by dedicated fishing, hunting, and foraging. Despite this the life expectancy of the Tsimane is sadly just 53 years old because of their lack of access to modern health care.
They live without plumbing or abundant fresh water or electricity. As such various diseases and gastro-intestinal or respiratory infections and parasitic infections are unfortunately commonplace.
The latest study published this year demonstrated that the Tsimane experience a 70% slower decrease in brain volume during their lives when compared to Western populations. It goes without saying that dementia and neurological degeneration (brain atrophy) is a huge issue in developed countries and perhaps studying the Tsimane could help provide a clue why this is the case.
Studies Revealed that the Tsimane have 70% Less Brain Atrophy
In order to obtain this information the study performed CT scans on 746 Tsimane participants (heaven knows what they thought of that!) to determine their brain volumes and brain atrophy. The authors stated that doing this involved the transportation of all these people from their remote villages to the nearest hospital (Trinidad), to undergo the scans.
To give some context this was an epic two-day journey travelling by rivers and roads. CT scans were then performed to assess brain atrophy in accordance with each participant’s age profile. These results were then compared to scans of individuals from three different population profiles across the U.S. and Europe.
As we mentioned earlier the results showed that the difference in brain atrophy loss was a staggering 70% less in Tsimane participants than those from the industrialized nations. This of course implies people from industrialised developed nations are much more likely to suffer neuron loss as part of the ageing process. Clearly this leads to loss of cognitive abilities and the possibility of Alzheimer’s and dementia.
The study suggested comments that ‘our sedentary lifestyle and diet rich in sugars and fats may be accelerating the loss of brain tissue with age and making us more vulnerable to diseases such as Alzheimer’s’. They concluded by stating that ‘the Tsimane can serve as a baseline for healthy brain aging.’ The importance of the study is that brain atrophy may be slowed substantially by the same lifestyle factors associated with very low risk of heart disease.