Time. Astronomers, philosophers, physicists, anthropologists, politicians, geographers, and theologians have all pondered the nature and meaning of time. Is it linear or cyclical? Is it reversible? (Put another way, can we go back in time?) Is time absolute and measurable, as it seemed to be to Isaac Newton and Galileo Galilei, or is it relative, as Albert Einstein theorized? Cynically, is it “what keeps everything from happening at once,” as science fiction author Ray Cummings wrote so memorably in 1923? Is time a cultural construct? Or is it a corollary to the second law of thermodynamics, under which disorder always increases? Why does time seem to go so much faster the older we get? Read More
Joshua Hinson’s first biological son was born in 2000. His son’s birth marked the start of the sixth generation that would grow up speaking English instead of Chickasaw, which was the primary language his ancestors had spoken for hundreds of years. Hinson was born in Memphis, Tennessee, and grew up in Texas. Other than a small handful of words, he knew almost nothing about his ancestral language—formally known as Chikashshanompa’. Hinson had a few pangs of sadness over the years about what was lost, but it didn’t really affect him—until his son was born.
As he counted the 10 tiny fingers and 10 tiny toes of his firstborn child, Hinson realized he had nothing to teach his son about his Native American roots. The only thing he had to pass on was his tribal citizenship card. Hinson wanted to bequeath more than just a piece of paper; he wanted his son to be a part of Chickasaw culture. He recognized that the most direct way to understand his culture was to speak the language. But to make that happen, Hinson had to start with himself. Read More
In a recent blog post, I focused on the Global Positioning System (GPS) and mused on how we ever got along without high-tech navigational aids. GPS units became common in cars and phones only in the last 15 years or so.
I remember when a road trip required a stop at the local American Automobile Association office to gather free maps of the planned route. Likewise, I remember when well-traveled road warriors had at least one dog-eared copy of a Rand McNally Road Atlas in their cars. Those days are gone, and I miss them. Read More
Eric Michael Johnson has a master’s degree in evolutionary anthropology focusing on great ape behavioral ecology. He is currently a doctoral student in the history of science at University of British Columbia looking at the interplay between evolutionary biology and politics. He blogs at The Primate Diaries at Scientific American, where this post originally appeared.
“Attachment (with respect to Martin Schoeller),” by Nathaniel Gold
My son will be 3 years old next month and is still breastfeeding. In other words, he is a typical primate. However, when I tell most people about this the reactions I receive run the gamut from mild confusion to serious discomfort. Their concerns are usually that extended breastfeeding could be stunting his independence and emotional development–the “Linus Blanket Syndrome” in the words of Michael Zollicoffer, a pediatrician at the Herman & Walter Samuelson Children’s Hospital at Sinai Hospital in Baltimore. Worse yet, they hint that it might even cause“destructive” psychosexual problems that he will be burdened with throughout his adult life. Could they be right? Was our choice “a prescription for psychological disaster” as Fox News psychiatrist Keith Ablow wrote in response to TIME magazine’s provocative cover article on attachment parenting? Just when is the natural age to stop breastfeeding?
One thing I’ve learned in my research on human evolution is that people are quick to assume that what they do is “natural” simply because they don’t know of other examples where things are done differently. The primate brain is a pattern recognition machine and is adapted to quickly identify regularities in our environment. But when we are presented with the same pattern over and over again it is easy to fall victim to what is known as confirmation bias, or coming to false conclusions because the evidence we use does not come from a broad enough sample. In order to avoid falling for this bias on the question of extended breastfeeding the best way forward would be to draw from the largest sample possible: the entire primate lineage.
In their classic paper, “Life History Variation in Primates” published in the premier scientific journal Evolution, the British zoologists Paul H. Harvey at Oxford and Tim Clutton-Brock at Cambridge published the most comprehensive data then available on the world’s primates. The variables they measured included everything from litter size and age at weaning to adult female body weight and length of the estrous cycle among 135 primate species (including humans). By analyzing the relationships between these variables, using a statistical approach known as a regression analysis, they identified striking patterns that held across primate taxa.
One especially strong correlation was that adult female body weight was closely tied to their offspring’s weaning age, so much so that knowing the first would allow you to predict the second with a 91% success rate. As a result, as anthropologist Katherine A. Dettwyler has shown in her book Breastfeeding: Biocultural Perspectives (co-edited with Patricia Stuart-Macadam), it can be calculated that a young primate’s weaning age in days is equal to 2.71 times their mother’s body weight in grams to the 0.56 power. This calculation predicts, given the range of female body sizes around the world from the !Kung-San of South Africa to the Arctic Inuit, that humans should have an average weaning age of between 2.8 and 3.7 years old.