Friday, January 3, 2014

Confused Article In The Hindu On Evolution, Disease And Paleolithic Lifestyles

What's up with The Hindu?.. another terrible article on science and evolution and biology by a medical professional soon after the recent ignorant hateful essay on homosexuality. Following reader outrage and detailed corrections that article on homosexuality has been retracted by The Hindu.

This one is by a cardiologist Dr Hegde. He begins thus:

Darwinian evolution has become outdated and its place is taken by the Lamarckian hypothesis of evolution by environmental compulsions. Darwin himself agreed with Lamarck but the neo-Darwinians, who have a big business interest in keeping the status quo, are at it even now. Even Erasmus was for environmental evolution long before Darwin came into the picture. Most of our pathophysiology of diseases is based on the Darwinian model unfortunately and it has to change for good. Earlier the better.

Darwinian evolution dead but kept alive by a conspiracy of big business... What utter rubbish! Later Dr. Hegde complains that "medical doctors do not go into evolutionary biology, even if a few of them go into biology". I hope he has counted himself in that list of medical doctors not getting into evolutionary biology for the above para is as uninformed as it gets.

Lets gets some terminology out of the way.

Darwinian evolution as the term is commonly used means adaptive evolution through mostly natural selection. Organisms in general produce more offspring than can possible survive due to limited resources. Organisms vary and if these variations are genetic will be inherited by their offspring. Offspring that have traits that enable them to utilize resources better will on average leave more offspring. Therefore favorable variation will spread through that population through generations. That is natural selection. The key here is that new variations that arise through processes like mutations are random with respect to the needs of the organisms but natural selection filters the favorable part of random variations.

Lamarckian evolution is also referred to as inheritance of acquired characteristics, a theory not originating with but attributed to the French naturalist Jean-Baptiste de Lamarck. Organisms respond to changing environments by making changes during their lifetimes to their physiology. These changes become (somehow) encoded in DNA of the germ line cells i.e. eggs and sperm and are passed along to offspring. Lamarck off course knew nothing about DNA. He simply proposed that changes acquired during one's lifetime are passed down. The canonical example is that the giraffe's neck became long by stretching to reach leaves on tall trees. This change was then inherited. There is really no evidence that changes to somatic tissues and cells can be passed on to the germ line cells. Recently, inheritance of acquired characteristics has gotten a lot of press by the advocacy of supporters of epigenetics which proposes that changes in gene expression in response to environmental stresses can be sometimes inherited without the DNA sequence of that gene being altered. This may indeed work in a few cases but the general understanding is that these changes do not last past a few generations and cannot play a role over evolutionary timescales. The mainstream thinking in evolutionary biology still firmly favors Darwinian natural selection as the main cause of adaptive evolution.

Having said that I fail to understand the connection between this first para and the rest of Dr. Hegde's article which is about how modern lifestyles and diets are adversely affecting our health. This is because our bodies have evolved in response to Paleolithic lifestyles and diets which were very different than our present ones and our bodies cannot adjust to these changes. Dr. Hegde relies on evolutionary biologist Daniel Lieberman's book The Story of the Human Body: Evolution, Health and Disease. You can read Dr.Lieberman's interview and listen to him on NPR's Fresh Air. This line of thinking is not new nor is it that controversial. An example is that in ancient times human diets had very little sugar content. Our physiology has evolved to manage a low sugar diet. Today's abundantly available sugar thus causes malfunctions like diabetes. Dr. Lieberman gives a long list of such ailments and a long list of human adaptations that evolved in response to our ancestral lifestyles. The problem is that Dr.Lieberman explains all these human adaptations as having resulted by Darwinian processes. He does not espouse Lamarckian explanations for them. Dr. Hegde though, confusingly having accepted Dr. Lieberman's thesis of an ancient evolutionary heritage built through Darwinian processes in  a mismatch with the modern world, then goes on to reject Darwinian mechanisms. He mentions the increasing prevalence of antibiotic resistance but ignores the fact that bacterial resistance to antibiotics has evolved through Darwinian natural selection.

I wonder what is the cause of this confusion. Dr. Lieberman says that cultural evolution has outpaced biological evolution and that natural selection is still going on but is slower than cultural changes. Cultural changes though can sometimes trigger biological evolution. One example is the evolution of lactose tolerance in adult humans.  Most mammals lose the ability to digest lactose in adulthood. However, the domestication of the cow and diary farming changed that in humans. Adults who by chance happened to have the ability to digest lactose benefited by the additional nutrition milk provided. Their better health translated into better reproductive fitness. This trait seems to have spread rapidly in dairy farming communities beginning around 8-10 thousand years ago. The mechanism for this change is natural selection and not a Lamarckian process. Maybe Dr. Hegde is equating rapid cultural shifts with a kind of rapid Lamarckian imprint on humans. Maybe what he is saying is that today Darwinian processes have stopped being important agents of change because they are too slow, yet he does not explain clearly his argument about why Lamarckian processes better explain evolution and why they promote new ways of thinking about disease.

Dr Hegde then closes with another bewildering passage on the origin of auto-immune diseases:

My own hypothesis of the origin of the many autoimmune diseases has its root in our mind. Whereas every cell in the human body, of which there are more than one hundred trillion in all, loves one another and also the cells of others in the world, our hostility towards fellow human beings confuses our cells. If that mental attitude deepens further into a trait, a time will come when our own cells start hating our other cells, auto-immune disease. I call this the you-me concept.

Deepak Chopra would have been proud of this pseudo-scientific mystical woo.

Finally, something of historical interest. Erasmus who Dr. Hegde mentions is Erasmus Darwin, Charles Darwin's grandfather. He was a 18th century polymath, one of the original members of the Lunatiks of Birmingham, an intellectual society founded in the British Midlands on the cusp of the Industrial Revolution. His life and times have been evocatively explored by Jenny Uglow in her beautiful book The Lunar Men- Five Friends Whose Curiosity Changed The World. Among Erasmus Darwin's many achievements was the book Zoonomia in which he published his theory of evolution which alluded to organisms changing in response to environmental cues.

Of more interest is the other reference Dr. Hegde makes- Did Darwin agree with Lamarck? This is a rather nuanced point and one of the best analysis of this question that I have read is by the philosopher of biology John Wilkins. His post Myth 3: Darwin was a Lamarckian is worth reading. The short answer is no. Darwin was confused in his thinking of how variation arises and is maintained in a population. He tilted towards the commonly held view that differences between individuals will get averaged out over time by the blending of variations over generations. So over time there will be no distinct variations left in the population for natural selection to work on. His way out of this quandary was to propose that commonly used traits are more strongly inherited than those less commonly used. This results in favorable variation spreading in a population. He however did not think that traits originated in response to environmental needs. The origin of traits was a mystery open to investigation.

The lament usually heard is that if only Darwin had read Mendel he would have seen the particulate nature of inheritance and understood how distinct variants can be maintained over generations despite the appearance of a blended form. This is one of history's "what if" questions which will remain unanswered. We do know that Darwin never really came to grips with the question of the origin of variability. Despite this, his idea of natural selection as the main agent of adaptive change has withstood the test of time.

Its death is reported with predictable regularity by professionals and by the media. Those reports though are always highly exaggerated.


  1. yeah..scary that a medical professional is writing this!..

  2. I have read a few of Dr Hegde's articles in the past and they have all been on similar lines, but none as bad as this theory of autoimmune diseases. Annoying for those suffering from one of them- specially if it had its onset in early childhood.

  3. L- its the first time I've read him and what a whopper!!

  4. I think this is from a section which is The Hindu's experiment with citizen journalism and they publish amateurish "blogger" stories. They are badly written and it would be a good idea for them to discontinue it.

  5. Slogan Murugan-- yes maybe although B. M. Hegde is not any amateur.. he is a celebrated cardiologist..this coming from a medical professional is shocking..