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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Chapter 7 opens with a real lemon, reported by the BBC: “For every alcoholic drink a woman consumes, her risk of breast cancer rises by 6 per cent.”

If every drink increased cancer risk by 6 percent, the disease would be almost universal. The more accurate summary (from a Cancer Research UK press release) is that “a woman’s risk of breast cancer increases by 6 per cent for every extra alcoholic drink consumed on a daily basis” (italics added).

But as Blastland and Dilnot point out, we’re still left in the dark: 6 percent of what? Is that a lot?

There are two problems here. The first is due to the fact that a woman’s risk of getting breast cancer is already a percentage. American women, for example, have a lifetime breast cancer risk of about 13 percent. So “increases by 6 per cent” can mean two different things:

1) It could mean an absolute difference of six percentage points. In that case you would add 13 percent and 6 percent to get a total of 19 percent risk.

2) It could also mean 6 percent of the original 13 percent risk. In that case, you would add 13 percent and 6 percent of 13 percent to get a much less dramatic 13.8 percent risk.

The convention in reporting risk is the latter. But the media often create a second problem by reporting the change but leaving out the baseline risk.

Take, for example, this passage from the New York Times: “Carriers of a single copy have a 15 to 20 percent greater risk of heart disease, while owners of two copies are up to 60 percent more likely to develop heart disease than people who have none.” (New York Times: May 3, 2007).

But the article never mentions what the baseline risk for heart disease is. If only 1 in 1,000 people with no copies of the higher-risk version of the SNP get heart disease—i.e., an individual’s chance is 0.1 percent—then having two copies increases one’s chance to 0.16 percent, or 1.6 out of 1000. That’s still a pretty scant risk.

But if heart disease were so common that even for people with no copies of the risky version, 60 out of 100 get heart disease, then those with two copies would have a whopping 96% chance (60 percent of 60 is 36) of getting heart disease. That’s a significant risk.

That’s why Blastland and Dilnot recommend that news stories report both baseline rate of disease and the rate after accounting for the risk factor. They also suggest converting percentages into a format that appears more personal: “In every 100 women, about nine will typically get breast cancer in a lifetime. If they all had two extra drinks every day, about ten would.”

We do something like this in 23andMe’s Gene Journal (now called Health and Traits), where we compare the average incidence of a disease to that for people with a specific genotype. Along with the additional context we provide, this allows our customers to better understand their data.

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