The father of the science of evolutionary medicine, Randolph (Randy) Nesse, has a favorite aphorism: “Medicine without evolution is like engineering without physics.” In the same way that it would be impossible to imagine building the Rosetta spacecraft, sending it 300 million miles to rendezvous with Comet 67P, and successfully deploying the Philae lander, chock-full with sampling instruments, without physics and specifically Newtonian mechanics, it proves similarly impossible, for instance, to get to the root of the horrifying scourge of Alzheimer's disease unless we ask deep and fundamental questions, informed by evolution, about what the alleged poisonous plaques of beta-amyloid protein are doing in the brain in the first place. Is amyloid pure pathology or does it have an vital evolved function in the brain? In this sense, Nesse has frequently claimed that the value of evolution to medicine is that it while it may lead directly to changes in medical practice or indeed to new therapies, more fundamentally its value lies in explaining why things are as they are. That is why Nesse argues that evolutionary biology should be the foundation and cornerstone for medicine as it should be for all biology. This book is an attempt to put yet more flesh on the bones of Nesse’s idea that evolution is the “physics” of medicine. I describe the evolutionary background to seven areas of human disease that are causing deep contemporary medical concern to explain why they exist in the first place—why things are how they are - and how evolution might help us to combat them. I hope it will leave readers with a new respect for evolution as the prime mover for the structure and function of human bodies, even if it does, on occasions, cause them to break down and drives us into ER!

Each chapter is built around the sometimes harrowing but always inspiring personal stories of people trapped in the disease process in question. Each chapter provides an evolutionary explanation for why the disease has come about, and each chapter shows how medical researchers, using powerful insights gained from thinking about disease in an evolution-informed way, are charting our way out of it.

How a modern version of the hygiene hypothesis - called the "old friends" hypothesis - explains why the Western world is riddled with allergic and autoimmune diseases, and what we can do about it.
How evolutionary theory explains why the battle between the different selfish genetic interests of mothers, fathers, and fetuses causes low fertility and can lead to diseases of pregnancy like recurrent pregnancy loss, preeclampsia and gestational diabetes.
What is the relationship between the fact that we have evolved to walk upright - our bipedalism - and a range of orthopedic illnesses?
Creationists have always used the example of the "irreducible complexity" of the human eye as the bedrock of their argument that God designed the human body, not evolution. Modern developmental biology, however, not only strongly rebuts creationism but explains the astonishing secret of how the recipe for eyes actually unfolds from within the developing eye itself, not from external influences, and is leading to cures for eye diseases like retinitis pigmentosa and macular degeneration.
How does cancer evolve so remorselessly towards malignancy that it is proving almost impossible to cure? Cancer evolution can be so extreme and drastic it is forcing us to re-write the rules of evolution by resuscitating a heresy from the 1940s.
Why are coronary arteries evolution's answer to feeding our powerful, muscular hearts with the food and oxygen they need and how has this led to the continuing pandemic of coronary heart disease?
Research into curing Alzheimer's disease has become hopelessly bogged down and billions of dollars have been wasted trying to turn the "amyloid hypothesis" into therapy. Can we use evolutionary thought to better explain why dementia comes about in a way that might lead to fresh hope for a cure?


Thursday, 9 July 2015

Prion Protein Protects against Epilepsy

Prion disease - more popularly known as "mad cow disease" - is a dangerous degenerative neuropathy. The prion is a so-called degenerate form of the PrPC protein which accumulates in diseased brains in a manner redolent of infection. The scientists here have discovered that the non-degenerate form of this protein has a protective effect on the brain in that it prevents the over-excitability of neural circuits which people experience as epileptic seizures. In other words, normal PrPC has an evolved neuro-protective role in the brain. There is a direct parallel here with Alzheimer's disease. The amyloid hypothesis - the dominant paradigm in Alzheimer's research - says that deposits of beta-amyloid protein build up in diseased brains and have a neurotoxic effect - killing off vast numbers of neurons and giving rise to dementia. This hypothesis avoids pointing out that, at certain concentrations, amyloid actually has evolved important protective functions in brains. First it is a powerful anti-microbial protein - it efficiently kills numerous types of pathogen. Secondly, at low concentrations it maintains transport of impulses across synapses from neuron to neuron. At slightly higher concentrations it restricts the passage of neural chattering. The phenomenon is called long-term potentiation - LTP. Learning and memory depends on LTP for the formation of lasting neural networks synonymous with the memory of learned behaviour or experience. But too much LTP can be a bad thing. If the passage of messages across these networks is unbridled it may result in the storm of activity we would experience as a fit or seizure. So, here, beta amyloid damps down the grid. Evolution frequently plays with fire in this way: pressing into service potentially damaging mechanisms or molecules for perfectly good reasons to help ensure the survival of young brains. But every upside can have a downside, as degenerate PrPC, and clumps of beta-amyloid, in older brains, can lead to dementia.

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