In this week’e Sunday Science…DNA and disease risks, how orca females make super grannies, another cancer immunotherapy success, bees, the world’s oldest hunting scene, and terrifying galloping crocodiles…

I’ve long been sceptical of genome-wide association studies (GWAs), which aim to determine if genetic variants between individuals increase the probability of inheriting certain traits, particularly disease traits. The reason I’m sceptical is that a lot of the ones I’ve seen pull out common critical genes which, if you disrupt them, are likely to cause a lot of problems regardless. Either that or the data is far too noisy to make solid conclusions. Now a new meta-analysis of two decades of GWS data based on variants called SNPs has concluded that, in most cases, your genes affect your chances of getting a disease by less than 5%.  While I’m at it, and this is something I feel like I bang on about a lot, but I’m going to bang on about some more: (1) risk is relative and (2) DNA isn’t everything. For (1), if a gene doubles your chances of getting a heart attack, that’s something to worry about, because heart attacks are very common (around 1 in 7 people in the US get them). Knowing that, you could reduce other risk factors, such as improving your diet and taking exercise. If a gene doubles your chance of getting motor neuron disease, this isn’t much to lose sleep over – you’ve gone from about a 3/100,000 chance to a 6/100,000 chance. Regarding (2), for example, there are many genes that increase your risk of cancer. Very few will increase it by as much as smoking and nearly all of these slight increases in risk could be offset by a healthy diet and exercise. So keep DNA in perspective and don’t buy one of those testing kits for Christmas! Original study published in PLOS One here (open access).

Young killer whales, or orcas, have a better chance of surviving if their grandmothers are around to help them; the grannies provide extra fish treats and knowledge of where to catch salmon. This is the first example in non-human mammals of what is known as the “grandmother effect”, previously only observed in humans. This evolutionary theory posits that the reason why females tend to live for many years after their reproductive lifespan is over is that they increase the chances of their grandchildren surviving, and has some good data to back it. It seems that this is something we have in common with these very intelligent, social animals. Original study published in PNAS here.

Another success in cancer immunotherapy: pembrolizumab, which has previously been shown to be effective in some head and neck cancers, demonstrated success for some men with advanced prostrate cancer for whom other treatment options had stopped working. Not all the men responded to the treatment, but just under 20% saw an improvement and 5% saw a huge improvement, with their tumours regressing, gaining years of extra life. There is more detail on these phase II clinical trial results here, and they are reported in full in the Journal of Clinical Oncology, here

The oldest rock painting depicting a hunting scene has been discovered on the Indonesian island of Sulawesi, and is estimated to be around 44,000 years old. Comparable paintings have only so far been found in Europe and are around half that age. The striking images depict local wildlife being hunted by small human-like figures, often with animal faces or tails. This would would suggest that the distinctly human capacity for narrative and imagination – for teling stories, in short – was already fully formed at this point. Original article published in Nature here (paywalled).

A really nice infographic explaining the vital role of pollinators, such as bees, in our ecosystems, and what’s behind their recent declines.

I have just discovered another reason to boost my fear of crocodiles: some of them can gallop, at up to 11mph. So not only can they get you on the water, if you’re not careful, they’ll chase you on the land! This trait appeared to have evolved in their “cat size” ancestors and probably was actually for running away, but I reserve the right to remain scared. Alligators and caimans can’t gallop, and the largest crocodiles are too heavy. Still, the Cuban crocodile, at up to 2m, can gallop. Original study published in Scientific Reports here (open access). There is a video of  (notoriously aggressive) Cuban crocodiles here with a rather terrifying gallop about 50 seconds in.

And finally, a selection of the year’s best science images, as chosen by Nature magazine. This week’s featured image is one of them, of “trumpet animalcules”, or stentors: single-celled freshwater protozoa. The blog will be on holiday for a couple of weeks now, returning mid-January.

Image Credit

Dr. Igor Siwanowicz, via Nature Publishing.

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