I spent the better part of my undergraduate career lugging around massive biology textbooks.  General biology, genetics, embryology: It didn’t matter, they all weighed a ton. I pored over endless chapters of text, highlighting the important sentences, always wishing for more photos, more diagrams, more graphs. A single well-made diagram or image was easier to understand than the preceding 10 paragraphs about the same topic.  I always wished that my textbooks were a little more visual and a little less wordy.  An added benefit, I thought, would be that I could shave a few pounds from my backpack.

My college days are long over. But my wish may have finally come true, in the form of a new graphic guide to genetics entitled The Stuff of Life: A Graphic Guide to Genetics and DNA, by Mark Schultz.  Published in December, it takes a more visual approach to presenting the most current knowledge on a particular branch of the biological sciences close to my heart: genetics.

The Stuff of Life is centered around a group of aliens who are trying to understand the genetics of all life on earth. These aliens are both rather ugly (the illustrator has drawn them to resemble sea cucumbers) and rather arrogant. They can’t seem to understand why a lowly, hairy primate has come to dominate the planet and make such amazing advances in science and technology. In the style of a comic book, with various windows and balloons leading us from the origins of the earth 4.6 billion years ago to modern day applications of genetics and DNA, it falls flat in oddly juxtaposing complex information and somewhat juvenile humor.

For anyone who hasn’t taken a college (or advanced high school level) biology class, the information presented will seem overwhelming at best, and confusing at worst. For those who are well versed in the biological sciences, the information may be understandable but the humor will seem trite and silly.  After the first few chapters of the cucumberesque aliens repeatedly exclaiming that they can’t believe humans have managed to understand how genes are passed down from parents to children, that they can’t believe humans have been able to sequence DNA, understand the genetics of cancer, and create genetically modified organisms, I began to dread their appearances. I stopped reading the sections focused on them, instead skipping to the parts that contained actual information. Once I did I began to enjoy the book much more.

The organization of the book is similar to a standard introductory genetics textbook.  It begins with a description of the structure of the cell, DNA, and how the genes housed within our DNA can determine thousands of physical traits.  Schultz then moves quickly forward, presenting important genetics concepts such as inheritance, dominant vs. recessive alleles, and why my cat has two different colors of fur.  Finally, he spends the last one-third of the book examining modern-day applications to the study of genetics.

The strategy works well by allowing the reader to understand the practical value of understanding the basic genetics concepts that were brought up in earlier chapters.  Indeed, having more applications-centric lectures during college might have silenced the students who never understood why this field is so important.  Undoubtedly, this section was written with the more general reader in mind.  It is easily the best section of the entire book.

Though the constant banter from the sea cucumber-like aliens should not interest anyone over the age of 10, this book would be of use to those currently taking an introductory course in biology, as it might help solidify more difficult concepts that might prove difficult to students.  For educators, this book could prove useful in providing fresh ideas on how to present some of the most important genetics concepts.

The uneven feeling I got from reading The Stuff of Life is something that must constantly be a fear for anyone who is trying to make science fun and accessible to the general populace.  Presenting such important topics as genetics and DNA that are easy for anyone to understand, scientifically accurate, AND enjoyable, is no easy feat.  And, while The Stuff of Life may have stumbled in some aspects, it is most certainly a noble effort, and may lighten the load in biology majors’ backpacks in the coming months.  I sincerely hope that Schultz continues with more volumes, though I could do without those sea cucumbers next time.

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Almost since the 1871 publication of “The Descent of Man,” in which Charles Darwin applied his theory of natural selection to the human species, biologists have argued over whether the dramatic series of evolutionary events that led to the emergence of Homo sapiens continues to this day.

Some have argued that culture and technology have eclipsed the powerful biological forces that shaped our species in its formative years. In their view the species, no longer faced with a daily struggle for survival, is adrift in an evolutionary Sargasso Sea.

“There’s been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve built with the same body and brain,” the famed evolutionary biologist Stephen J. Gould once said in an interview.

In their new book “The 10,000 Year Explosion,” anthropologists Henry Harpending and Gregory Cochran argue the contrary position. They claim that in fact, far from grinding to a halt, human evolution has accelerated dramatically since the origins of agriculture about 10,000 years ago.

“We intend to make the case that human evolution has accelerated in the past 10,000 years, rather than slowing or stopping, and is now happening about 100 times faster than its long-term average over the 6 million years of our existence,” they write.

In evolutionary terms, 10,000 years is no time at all — about 400 human generations. Rabbits can go through 400 generations in not much more than a century — can you imagine rabbits being substantially different than they were 100 years ago?

Far from ending the chain of dramatic evolutionary changes that led to upright walking, advanced cognitive abilities and spoken language, Cochran and Harpending argue, the adoption of agriculture so dramatically changed the human environment that a new wave of genetic innovations flourished. These new genetic variants thrived because they helped people cope with the challenges an agricultural way of life presented, such as the shift to a low protein, high carbohydrate diet; the creation of an organized, stratified society and the rise of infectious diseases in response to increased population density.

In fact, many of the genetic variations that 23andMe provides information about are relics of those evolutionary changes. The SNP that confers lactose tolerance, for example, appears to have arisen in Europe about 8,000 years ago among the first people to herd cows and other milk-producing animals. The lactose-digesting variant quickly spread throughout the parts of Eurasia that were ecologically suited to pastoralism.

There are also a number of genetic variations covered by 23andMe that cause physiological problems when two mutated copies are present, but provide protection against infectious disease when a person has one of each version of the gene. For example, the genetic variations that cause sickle cell anemia and G6PD deficiency confer resistance to malaria. Geneticists call this situation balancing selection; over the entire population, the reproductive cost to those who end up with the genetic disease is outweighed by the benefit to others who are resistant to the infectious one.

At the end of the book, Cochran and Harpending make the controversial argument that balancing selection is responsible for the increased incidence of a number of genetic diseases among people of Ashkenazi Jewish descent — and for their higher intelligence relative to other groups.

The authors do raise some interesting points about the anomalously high frequency among Ashkenazi of genetic disorders that stimulate the growth of neurons in the brain. And they cite studies that have shown increased intelligence among people with some of these diseases.

But genetic explanations for between-group differences in intelligence are best taken with a whopping dose of skepticism. Even the definition of intelligence is a matter of intense debate, not to mention the degree to which it can be inherited through genetics. in the end, their case is little more than a just-so story.

In telling it Cochran and Harpending blunt the rest of their book’s powerful message: human evolution is not over by a long sight.

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For more than a century anthropologists have studied the multitude of cultures and ethnicities that exist across the globe, delving deep into the various ways that populations develop their own unique identities. With the development of genetic anthropology over the last 15 years, scientists have begun to examine whether these cultural identities align with a population’s genetics. How do we as humans differ genetically from one another, and how have these differences arisen throughout our species’ history? This fascinating question is tackled by Steve Olson in Mapping Human History: Discovering the Past through our Genes.

Olson is well suited to explain the complex genetic history of our species. He has worked for the National Academy of Sciences, the White House Office of Science and Technology Policy, and written several books and articles for general audiences on human genetics. While researching this book he interviewed a large number of anthropological geneticists. He uses his experience in science communication — as well as those interviews — to tell the story of Homo sapiens, beginning in Africa and touching on nearly every major geographical region in the world.

Olson starts his exploration of our species’ genetic history where it began, in Africa. He begins by describing some of the most isolated and interesting ethnic groups — the so-called Bushmen of southwest Africa and the Kalahari Desert. This well known group of hunter-gatherers has interested anthropologists and geneticists alike for many decades. The Bushmen are relatively isolated, maintaining a hunter-gatherer lifestyle even as many populations around them have taken on new lifestyles. They also speak languages that are famous for their ‘click’ sounds. Belonging to the Khoisan language family, these languages are believed to be some of the most ancient still spoken among humans.

Olson uses examples such as the Bushmen to delve deeper into the science of genetic ancestry. He clearly explains how scientists use DNA to trace both maternal and paternal ancestry, similar to what we at 23andMe do as part of our Personal Genome Service™. After spending time discussing Africa Olson moves on, tracking our species’ prehistoric movements into the Near East, Asia, Europe, and even the Americas. He also spends time discussing some of the most interesting genetic questions about our species, such as the origins and migrations of the Jews throughout history, and how changes in languages can sometimes be connected to genetic changes.

The final portion of Mapping Human History investigates more closely the cultural and ethnic issues that have arisen over the past ten years because of studies that examine the genetic ancestry of specific populations. Some Native American groups, for example, protest studies such as these because they conflict with their own tribes’ creation stories. However, Olson argues this research should actually be applauded, because “the study of genetics has now revealed that we are all linked…. We are members of a single human family, the products of genetic necessity and chance.”

Mapping Human History is, overall, a good foray into our species’ genetic past and how genetics studies can reveal many things — both about how we are different, and how we are the same. Olson peppers his arguments with engaging anecdotes, such as the story of a female researcher in South Africa with mixed heritage, or how the peopling of Hawaii led to such unique genetic diversity among its current inhabitants. These anecdotes would be welcome for any general reader, making the concepts Olson discusses more real and accessible to a general audience.

There are many books that deal with genetic ancestry, and this one does cover many of the same topics as countless others. But what distinguishes Mapping Human History is its focus on genetic versus cultural and ethnic divisions in our societies. This alternative angle may prove interesting to general audiences with non-science backgrounds, as Olson brings in issues such as race relations and cultural and ethnic diversity that are relevant to many people.

This text would prove an appealing read for 23andMe customers looking to put their own genetic information into a global context. In addition, it would be well-suited for anyone interested in how our species has evolved and expanded over the last few hundred thousand years, and how these past migrations have shaped the ethnic and cultural identities that exist today across the globe.

Mapping Human History: Discovering the Past through our Genes
Steve Olson
2002
New York: Hougton Mifflin Company

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If anybody could turn the history of genetic anthropology into a page-turner, it would be Bryan Sykes. Sykes, Professor of Human Genetics at the University of Oxford, has spent the better of part the last 25 years decoding the mystery of our species’ genetic ancestry through mitochondrial DNA analysis. He recounts his work in his 2001 book, The Seven Daughters of Eve: The Science that Reveals our Genetic Ancestry.

But Sykes doesn’t simply relate the major discoveries in the field. He goes one step further by breathing life into each of the seven major mitochondrial DNA clusters that are common today in European populations.

The Seven Daughters of Eve can be divided into two major parts. In the first, Sykes discusses some of his most fascinating work. He relives how he and his colleagues extracted ancient DNA from the 5,000-year-old Ötzi the Iceman, examines his work on understanding the origins of the Polynesians, and tells how he and his team discovered the true fate of Tsar Nicholas II and the Romanovs. With each story, Sykes easily manages to explain the scientific details behind his conclusions in a way that nearly any reader can comprehend.

23andMe customers will be most interested in Sykes’ explanation of how mitochondrial DNA can be used to trace individuals’ maternal ancestry. Mitochondrial DNA (mtDNA) is a small segment of circular DNA that is found in tiny organelles called mitochondria. It is believed that hundreds of millions of years ago, mitochondria were free-living bacteria who invaded more advanced cells and never left. Now, they are an integral part to every cell. For people like Bryan Sykes, however — not to mention 23andMe customers who are interested in their ancestry — mitochondria are mostly important for what their DNA can tell us.

Because of the way fertilization takes place, mitochondria (and thus mtDNA) are only passed from mother to child, like a kind of “matrilineal surname.” In the same way that surnames can change gradually over generations, so too does mtDNA. So while two siblings are almost certain to have identical mtDNA, people whose most recent common maternal ancestor lived thousands of years in the past are likely to bear substantially different mtDNA signatures.

As it turns out, the different mtDNA patterns found in populations around the world can be organized together into a global family tree. At the tips of the tree are present-day human populations from around the world. At the root of the tree is the common mtDNA ancestor of every human alive today, a real woman who lived in Africa about 175,000 years ago.

As with any family tree, some people are more closely related than others. Scientists have given these more closely related clusters, or ‘haplogroups,’ specifically designated letters. There are seven such haplogroups (and thus, seven letters) among people of European descent — U, K, H, V, X, T, and J.

These seven haplogroups form the basis for the second part of Sykes’ book. As a way of making them seem more personal to the reader, he gives them each a name. For example, haplogroup U becomes Ursula, X become Xenia, H becomes Helena, and so on. These are the so-called “Seven Daughters of Eve.”

Sykes uses these names to create stories based on where in Europe the descendants of each “daughter” are concentrated. In a chapter on haplogroup K (Katrine), he relates the domestication of wolves. The chapter on haplogroup J (Jasmine) is dedicated to the beginnings of agriculture in the Near East more than 10,000 years ago.

Sykes concludes his journey into our species’ genetic past by explaining why he feels it important to understand genetics from a personal standpoint. He writes, “I like this kind of genetics because it puts the emphasis back where it belongs: on individuals and their actions.” There are so many stories hidden in our genes, he reasons, and it is best to tell them to the public in this fashion.

This book is not without flaws. The anecdotes about Sykes’ research in the field are, by definition, centered on how he was the major player in each discovery. As a result, many important players in the field are marginalized or left out completely. In addition, the dramatic benefit of assigning each haplogroup its own story comes at the expense of accuracy and completeness. For example, haplogroup J (Jasmine) is not the only one associated with the origin and spread of agriculture form the Near East to Europe; but in The Seven Daughters of Eve, it is the only one mentioned.

However, simplifying and romanticizing genetic anthropology does make for a good story – which was Sykes’ goal in the first place. Indeed, Sykes has discovered many amazing stories in his years of research at Oxford, and The Seven Daughters of Eve proves to be an engaging journey that can be enjoyed by general audiences and genetic ancestry enthusiasts.

The Seven Daughters of Eve: The Science that Reveals our Genetic Ancestry
Bryan Sykes
2001
New York: W.W. Norton & Co.

Photo by SCM Studios/istockphoto

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