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?


Friday, 31 July 2015

Expanding the brain: Research identifies more than 40 new imprinted genes

It's imprinted genes day! This companion piece to the earlier post involves the work of Catherine Dulac, at Harvard. They have annotated over 100 imprinted genes in the brain, including 40 newly-discovered genes. "We looked at a single brain area—the cerebellum—in a very rigorous way, and found 115 imprinted genes, more than 40 of which were brand-new," Dulac said. "That is a 30 percent increase in the number of known imprinted genes in the mouse, which is significant, but the other important idea this paper explores is the notion that these imprinted genes provide a way for the diversity of the brain to flourish. In addition to the diversity in our genetic sequence, the question of who are we inheriting these genes from adds to the diversity we see across a population."

Many are specifically imprinted in the brain and are not imprinted in the rest of the body and many are proportionately imprinted, not either switched on or off. "So there may be 70 percent expression from the maternal allele, and 30 percent from the paternal," Dulac said. "It's not all on or all off." To understand whether these biases have biological significance, Dulac and colleagues targeted a gene called Bcl-X, which, in the adult cerebellum, is expressed 60 percent from the paternal genome and 40 percent from the maternal, and helps prevent cell death.

"Our question is, 'Does the brain care about that bias?'" Dulac said. "If it doesn't we could remove either copy of the gene, and it shouldn't matter. But if that bias ― even though it's not particularly strong—is important, when we remove the more highly expressed copy of the gene, we should see a different phenotype emerge. "When we did this, the results were spectacular. When we removed the paternal copy, we obtained mice with brains that were 15 to 20 percent smaller than mice in which we removed the maternal copy or mice which had both copies."

No comments:

Post a Comment