There are reasons you look the way you do.
- A panel of eight experts in the evolution of the human face have collaborated on a new summary of how we've changed.
- Their paper promotes the importance of social interaction as a factor in the structure of our visages.
- We can visually express more than 20 categories of emotion. Early humans not so much.
Your face is not yours alone — written there are traces of your parents, grandparents, and ancestors. Now a paper published in Nature Ecology and Evolution makes an even broader case. Your face, that so-familiar visage you see in the mirror each day, contains a living, breathing history in its features of humankind's evolution from the earliest African hominids to, well, you. What's revealed, its authors say, is that the ability to communicate and thus thrive in social contexts deserves to be given more credit as a key factor in the evolution of our appearance.
A gathering of face experts
Image source: Rodrigo Lacruz
The new paper is the work of eight of the world's foremost experts in the evolution of the human face. At its heart is an attempt to answer a very basic question: Why do we look so different from other, extinct hominins, as well as our primate cousins such as chimpanzees and bonobos? Our faces have gotten smaller over time. The question is why? "We know that other factors such as diet, respiratory physiology, and climate have contributed to the shape of the modern human face," says Paul O'Higgins of the University of York, one of the experts involved, "but to interpret its evolution solely in terms of these factors would be an oversimplification."
University of Arizona's William Kimbell, also involved in the study, puts it this way: "We are a product of our past. Understanding the process by which we became human entitles us to look at our own anatomy with wonder and to ask what different parts of our anatomy tell us about the historical pathway to modernity."
The shrinking human jaw
Our changing diet is thought to be the primary factor in the reduction in size of our jaws that began as we started cooking and cutting-up our foods about 10,000 years ago. We no longer needed such crushing mandibles to make our way through our omnivorous diet, and the benefit of strong chewing capabilities became less of a factor in natural selection. It's likely no coincidence that the trend toward a smaller chin accelerated with advent of the beginning of the agriculture.
As far as other areas of the face, the story is even more interesting. It seems that our transition to community living mandated a greater ability to communicate well. While the scientists hypothesize that the strong brows of Homo erectus and the Neanderthals were effective for communicating aggression, strength, and domination — as we see in the great apes — these signals were no longer as beneficial to humans as we began to gather into communities.
"We can now use our faces to signal more than 20 different categories of emotion via the contraction or relaxation of muscles", O'Higgins says. "It's unlikely that our early human ancestors had the same facial dexterity, as the overall shape of the face and the positions of the muscles were different."
The changes to our physiology have endowed us with the ability to communicate far more effectively in groups, and it's easy to imagine how getting along with others led to a greater chance of reproducing. Before the arrival of language, in particular, the ability to facially communicate friendliness, sympathy, and other feelings was critical in gaining others' acceptance.
Are we there yet?
O'Higgins looks back, and forward. Image source: University of York
According to O'Higgins, most likely we're not done evolving. "There are limits on how much the human face can change, however. For example, breathing requires a sufficiently large nasal cavity. However, within these limits, the evolution of the human face is likely to continue as long as our species survives, migrates and encounters new environmental, social and cultural conditions."
So, that face. Your face. It's part of a long, ongoing story starring your ancestors and their ancestors. It's an interesting way to see that person looking back at you from the mirror.
Researchers at Human Longevity have developed technology that can generate images of individuals face using only their genetic information. But not all are convinced.
What if a computer could generate a realistic image of your face using only your genetic information?
That's precisely the technology researchers at Human Longevity, a San-Diego based company with the world's largest genomic database, claim to have developed. The team, led by genome-sequencing pioneer Craig Venter, reported their findings in a controversial paper published in the journal Proceedings of the National Academy of Sciences.
To train the A.I. to generate facial images, the team first sequenced the genomes of 1,061 people of various ages and ethnicity. They also took high-definition 3D photos of each participant. Finally, they fed the photos and genetic information to an algorithm that taught itself how small differences in DNA relate to facial features, like cheekbone height or protrusion of the brow. The algorithm was then given genomes it hadn't seen before, and it used them to generate images of the individual's face that could be reliably matched to real photos.
Well... sort of.
The team successfully matched eight out of ten images to the real photos. However, this rate fell to just five out of ten when researchers analyzed participants of only one race, considering facial features differ slightly by race. Judge for yourself how well the algorithm did:
The potential applications of this technology are especially intriguing for fields like forensic science — what if investigators were able to use genetic information left at a crime scene to “see” the perpetrator?
Interesting as the applications may be, Human Longevity is more concerned with the implications its findings has on privacy in genomics research, namely that technologies like this could be used to match people's thought-to-be anonymous genetic information to their online photos.
“A core belief from the HLI researchers is that there is now no such thing as true deidentification and full privacy in publicly accessible databases,” HLI said in a statement.
Privacy concerns seem to be widely shared in the community. But some scientists say that the paper is misleading. One reason is that the Human Longevity researchers already knew the age, sex and race of the participants — demographic information that could have been used to achieve the same matching rate without using the computer-generated photos at all.
“I don't think this paper raises those risks, because they haven’t demonstrated any ability to individuate this person from DNA,” said Mark Shriver, an anthropologist at Pennsylvania State University in University Park, in an interview with Nature.
Jason Piper, a former employee of Human Longevity, took issue with what he considered a lack of accuracy in the images, writing on Twitter that:
“everyone looks close to the average of their race, everyone looks like their prediction.”
But perhaps the most exhaustive criticism came from computational biologist Yaniv Erlich, who published a paper entitled Major flaws in "Identification of individuals by trait prediction using whole-genome sequencing data, part of which reads:
“The results of the authors are unremarkable. I achieved a similar re-identification accuracy with the Venter cohort in 10 minutes of work without fancy face morphology...”
Just days later, the team behind the original paper issued a rebuttal, titled simply No major flaws in "Identification of individuals by trait prediction using whole-genome sequencing data.
(It may seem mundane to those outside the field, but it's a pretty vicious beef in the scientific community at the moment, as seen by the "shots fired!" and "I'm gonna grab my popcorn..." comments under both papers.)
Access to genomics data
Underlying this whole debate is a question of access. Genomic data is used across various fields of study, but perhaps most importantly in research that seeks to combat diseases. In an interview with Nature, Piper said that Human Longevity has a vested interest in restricting access to DNA databases because it's a for-profit company that's trying to build the largest genome database in the world.
“I think genetic privacy is very important, but the approach being taken is the wrong one,” Piper said. “In order to get more information out of the genome, people have to share.”
Rather than privatizing and restricting access to genomic data, Piper said that a better solution would be to make data public while using techniques that still allow individuals to remain anonymous.