As we are passing the one-year mark of the Covid-19 pandemic, it is difficult to wrap my head around the long term consequences of this catastrophe. To date, this pandemic has infected over 142 million people worldwide and withered the global economy by 4.4 percent in 2020. It is far too early to contemplate the ending of this pandemic as we are still in it, writing our story as it is unfolding before our eyes, navigating our way on a path that none of us has walked before. As for guidance, we are looking back into history, trying to make sense of this unprecedented time by reminiscing the parallel incidents of our past, trying to cope by predicting the possible impacts of this moment on our future. This is a story about my erudition, as a father, scientist and Bangladeshi, pondering on my past as I try and plan for the possible imminent future.
Part one: Decoding DNA to understand my past
Around 600,000 years ago, somewhere in Africa, a group of hominins (human species and all our immediate ancestors) evolved to become Neanderthals, close cousins to us, the Homo sapiens. They left Africa about 350,000 years or more ago for Eurasia. For more than 300,000 years, Neanderthals lived in Europe and Central Asia until they became extinct, around 40,000 years ago. Contrarily, our Homo sapien ancestors, who left Africa approximately 100,000 to 60,000 years ago, eventually conquered the world.
Deoxyribose Nucleic Acid or DNA works as the molecular blueprint of all living things. This unit of inheritance is passed on generation-to-generation, responsible for putting my great grandfather's nose on my son's face even though they've never met each other. Our DNA consists of over three billion of four different chemicals: adenine "A," thymine "T," guanine "G," and cytosine "C," which uniquely combines to create a DNA blueprint for each individual.
When the entire human DNA was decoded 15 years ago, it ushered in a new era of genetic medicine. In 2010, the first draft of the Neanderthal genome sequence was published. One of the surprising discoveries in decoding the Neanderthal DNA sequence was the evidence of interbreeding between Neanderthals and the ancestors of Homo sapiens. By combining next-generation sequencing technology with rigorous statistical modelling, scientists can trace back the archaic DNA in the genome of present-day Homo sapiens, including my own, and provide convincing scientific evidence of such propagation. About one to four percent of the DNA of all Homo sapiens outside of the African continent contains pieces of DNA from Neanderthal, also known as variants.
I was born in Dhaka to Bangladeshi parents and immigrated to the USA at the age of 19 to pursue my education. As a cancer biologist, I consider myself a fact seeker of human biology—spending most of my adult life chasing the mystery of genetic disease to mitigate the suffering of cancer patients. My inquisitive nature as a scientist was the only provocation behind the decision to have my own DNA analysed as soon as such testing was made available to the public in the United States. I chose 23andMe, a widely used DNA testing service to decode my DNA.
As I had anticipated, the test suggested that 100 percent of my ancestry is Bengali. My paternal haplogroup (family of lineages that share a particular set of DNA signature or variant) is O-Page23, a long line of men who lived in eastern Africa 275,000 years ago. This is a rare haplogroup among 23andMe customers as only one in 82,000 shares this same haplogroup assignment. My maternal haplogroup is M30d1, which originated from a single woman whose lineage lived in eastern Africa from around 150,000 to 200,000 years ago. While the M haplogroup is widespread throughout South and East Asia, the degree of diversity of the M haplogroup is the highest in the Indian sub-continent.
My DNA test revealed that out of the 2,872 Neanderthal variants examined by 23andMe, 196 variants in my DNA belong to Neanderthals. This is about five percent more than the other 23andMe customers. For the past 10 years, extensive research has been conducted to understand the functional consequence of the Neanderthal DNA in our genome and how it may influence human evolution. Scientists have utilised genome-wide association or GWAS, a method used in genetic research to examine if a specific genetic variant is related to any trait or disease.
Studies have linked different Neanderthal variants with particular genes, which make up a small section of our DNA. These genes contain the instructions for specific protein—molecular produce by our body by following the instructions written in a gene within our DNA. Protein carries out all the functions for genes. In the presence of a Neanderthal variant, the function of a protein can be altered, which leads to individual functional traits, ranging from hair colour and skin to neuropsychiatric disorders and immune system functions. According to the initial 23andMe analysis, none of my Neanderthal variants are associated with any known Neanderthal traits.
But discoveries in this field are evolving by the minute. In fact, in just one night, the perception concerning my DNA carrying harmless Neanderthal variants, as it was initially reported to me, was suddenly altered in a significant manner.
Part two of this article will be published tomorrow.
Atique U Ahmed PhD is Associate Professor of Neurological Surgery at Northwestern University Feinberg School of Medicine. His Twitter handle is @atiqueahmedphd.