Posted in biology, physics, technology

Humans vs Neanderthals – the mammoth competition that ended in extinction

After thousands of years, the reason for the Neanderthal’s extinction has finally come to light. Using isotopic analysis, it was found that both ancient humans and the Neanderthals were in direct competition for their main food source – woolly mammoths.

The first anatomically modern humans are thought to have colonised Europe around 43,000 years ago, forcing the Neanderthals into extinction approximately 3,000 years later. So, why did Homo sapiens succeed where the Neanderthals could not? There are many hypotheses, but by far the most common is that the diet of anatomically modern humans was more varied and flexible, allowing them to consume fish. However, a new study by the Senckenberg Research Institute and the Natural History Museum has blown this out of the water.

The hypothesis that early humans had a more varied diet has been fuelled by the observation that they had a higher abundance of 15N in their bone collagen when compared with Neanderthals. This difference was chalked up to the addition of freshwater fish to the diet, a conclusion that has been refuted by  Prof. Dr. Hervé Bocherens and his colleagues at the University of Tübingen.

There are two main explanations for the presence of 15N in ancient human remains – a high concentration of 15N in the natural environment, especially concentrated in the meat of large herbivores whose meat makes up the majority of the diet, or a significant dietary contribution from a single prey with higher 15N abundance than prey usually found at archaeological sites (e.g. fish or mammoth meat).

Until recently, it has not been possible to distinguish between the dietary impact of freshwater fish and mammoth as both are known to have high 15N abundance and comparable levels of the 13C isotope. Due to the overlapping isotope abundances, accurate estimation from collagen alone was not possible. However, due to recent advances in stable nitrogen isotope analysis on individual amino acids, it is possible to identify the exact origin of the proteins consumed by the ancient humans.

In the study, the remains of three anatomically modern humans were examined. Found in the Belogorsk region of south Crimea, the remains were examined for phenylalanine (as a baseline) and glutamic acid (as an indicator of trophic position). Alongside the humans, the fossils of variety of prey animals found during the excavation were also investigated. Using the percentage ratio of the 13C to 15N isotopes present in the proteins of both the ancient humans and their prey, the scientists could establish the main components of their diet. Using this data, it was found that mammoth meat made up around 40-50% of the Homo sapiens’ diet. Isotopic studies of western European Neanderthals have also pointed to a significant consumption of mammoth meat, placing them in direct competition with the ancient humans.

This fierce interspecies competition for resources placed the Neanderthals under extreme stress. Without unrivalled access to their main food source – woolly mammoths – they were unable to forage enough food to survive. Whether due to superior hunting ability, increased brain size or other factors, Homo sapiens emerged on top. Without competition, humans thrived and have persisted until today. However, this is not the case for the poor woolly mammoths.

Tabitha Watson

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Posted in biology

Could yoga be used to treat depression?

A series of studies into the antidepressant effects of yoga have returned positive results.

Since its rise to western popularity in the 1980s, people have enthused about the health benefits of yoga. One of the most frequently touted claims is that practicing yoga can aid your mental health. However, empirical evidence to back up these claims has often been difficult to find.

Lindsey Hopkins, a researcher at the San Francisco Veterans Affairs Medical Centre, has set out to plug the gap. Her study focusses on the antidepressant effects of hatha yoga, a branch of the discipline that emphasises physical exercise, meditation and breathing exercises in order to enhance wellbeing. Twenty-three male veterans participated in the study, attending twice-weekly classes for eight weeks. The result? All the participants with elevated depression scores before the program experienced a significant decrease in symptoms after their involvement.

Nina Vollbehr, who works at the Centre for Integrative Psychiatry in the Netherlands, has also investigated yoga’s antidepressant potential. Her first study involved tracking twelve patients, each of whom had experienced depression for an average of eleven years, as they participated in nine weekly yoga sessions. The participants’ levels of depression, anxiety, stress, rumination and worry were measured before they took part, immediately after the program and then again four months after the program ended. The data collected showed a decline in the symptoms of anxiety, stress and depression throughout the program, the benefit of which persisted for the four months afterwards. On the other hand, rumination and worry did not decrease during the program. However, a slight reduction in rumination and worry symptoms was found in the four month follow up.

Vollbehr’s second study compared yoga to another relaxation technique. In it, seventy-four mildly depressed university students were given thirty minutes of instruction on either yoga or relaxation. They were then asked to perform the same exercises at home for eight days, with the aid of a video. Immediately after the study, it appeared that both yoga and relaxation both had the same positive effect, but the two month follow up indicated that the yoga group had significantly lower scores for depression, anxiety and stress than those who had followed the alternative relaxation program.

Now, it is clear that the sample sizes in the studies are small and that the research into yoga as a treatment for depression is still very much in its preliminary stages. However, according to Jacob Hyde, a military psychologist at the University of Denver, the concept of yoga as a complementary or alternative mental health treatment certainly seems promising.

Tabitha Watson

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Posted in biology, science

How do we hear?

In order to hear the world around us, humans and other mammals rely on vibrations travelling in the air. To interpret these vibrations, the ear has evolved a complex system of canals and tiny hair-like protrusions, all working in harmony to generate sound as we know it.

The ear is a complex structure composed of three distinct parts, each with separate functions. The outer ear (or pinna) is the external section that protrudes from the side of the head. Responsible for the placement of sounds in relation to our bodies, the complex arches and valleys funnel vibrations into the ear canal and create a three dimensional soundscape.

Once the vibrations begin to move down the ear canal, they enter the middle ear. This section is composed of the auditory canal, which terminates at the eardrum (also known as the tympanic membrane). The eardrum is then attached to three tiny bones called ossicles, surrounded by a small pocket of air. Individually, these bones are the malleus, incus and stapes (or alternatively, the hammer, anvil and stirrup). The ossicles are then attached to a fluid-filled structure called the cochlea. It is here that the inner ear begins.

The primary function of the cochlea is to convert vibrations into electrical impulses to be sent down the auditory nerve and interpreted by the brain. In order to change the vibrations to impulses, a rather ingenious method is employed. Once the vibration reaches the cochlea from the ossicles, it travels down the basilar membrane whereupon it is detected by approximately 16,000 to 20,000 hair-like cells called cilia. These cilia are attached to a specialised part of the ear canal called the Organ of Corti, and it is here that the raw vibrations are converted to nerve impulses and passed along the auditory nerve to the brain. This is achieved by the deformation of the cilia – as they are moved by the vibrations, specialised ion channels are pulled open and the resultant influx of potassium and calcium ions depolarises the cells and produces an action potential.

So how are humans able to hear such a spectrum of different sounds and pitches? Well, it’s all down to the tapered shape of the cochlea. Due to their individual amplitudes, different frequencies of sound wave peak at different times as they travel down the ear canal. As higher frequency waves have larger amplitudes, they are not able to travel as far as lower frequency waves. Due to this, each section of cilia is sensitive to a particular frequency of wave – this is what enables the detection of such a vast spectrum of sound.

Tabitha Watson

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Posted in biology, science

Is napping bad for you?

Unfortunately, it is often the case that the most enjoyable things in life are also the worst for you. Sweets, coffee, alcohol; the list seems endless. One of the most enjoyable things in life (at least for a student), is a cheeky nap after a particularly trying lecture. However, is it good for you?

There is conflicting evidence surrounding the concept of napping – some suggest that a brief siesta after your 9am lecture could help you lose weight and even boost brain activity, whereas others think that too many naps could increase an individual’s risk of developing Type 2 diabetes. So, which is the truth?

A study conducted at the University of Tokyo in Japan found that those who napped for longer than an hour per day were 45% more likely to contract Type 2 diabetes than those who did not nap or who napped for less than an hour. Despite this seemingly damning evidence, all is not lost for those who enjoy a longer snooze. It is very likely that the data gathered by the Japanese research team could have been influenced by external factors not recorded in the distributed questionnaire – in fact, it is almost certain. A more recent research project presented at the European Association for the Study of Diabetes suggested that the correlation between obesity and napping is likely to have influenced the apparent link to diabetes. They argued that the existing obesity epidemic and not the act of napping itself was to blame for the raised diabetes risk.

The claim that napping can help with weight loss can also be swiftly debunked: on average, people who sleep around 5 hours per night tend to gain less than 2kg of weight per year, which is on par with those who sleep around 7 hours per night.

After examining both sides of the argument, it appears that napping is a fairly neutral pastime. When the evidence is weighed up, the correlations between extra sleep and the proposed health benefits and/or detriments seem to be built on rather spurious connections, vastly influenced by external variables. Finally, a pleasure that can be enjoyed sans-guilt.

Tabitha Watson

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