Q:Hello. Since you're the only science tumblr I follow I thought I would ask you this question. If an interracial couple were to marry, and have children, and their interracial children had interracial children, and so on, how many generations would it take before either the maternal or paternal ethnicity would be completely eliminated? (i.e. if it was a black and white couple and their mixed child married an asian, and their mixed child married an hispanic, and so on.)
Hi there! Thanks for your question. Unforch, this question isn’t really answerable.
Ethnicity and race are social constructs, not useful genetic traits that we can (or should) use to differentiate people. Ethnicity and race can’t “dilute” out (in a genetic sense), because you can’t point to a genome and say “that’s the Hispanic gene” or “There’s the sequence that makes you Asian.” Yeah, we can point to genes that influence skin color or facial features, but that’s not race. It’s biology.
That doesn’t mean that we can’t track genetic differences based on geography and its associated populations, though. We can, and we do. For instance, if we compared the genome sequences of indigenous North, Central and South American populations to, say, Asian and European genome sequences, we would see that the original Americans are more closely related to Asian populations. This matches up to geological studies that suggest that there once existed a Siberian land bridge, and allows us to make hypotheses about human migration patterns across the Earth (not all of those migrations have been voluntary, mind you).
We can, and have, done the same analysis by comparing modern and ancient samples from place X with modern and ancient African DNA, which is how we know that we the first members of our species left Eastern Africa about 70,000 years ago to settle the four corners of the Earth (which has no actual corners, of course).
However, like quick-drying cement, this analysis gets really hard, really fast (insert your own dirtier joke there if you like). Genetic fingerprints get jumbled thanks to the huge amount of genetic crossover that happens as part of our meotic sexytime, and because humans have interbred … a lot. Not in a gross (and genetically dangerous) “banjo player in Deliverance” way, but in a “we’re all related” way. We only have to go back 2,000-4,000 years before we find a person who is a common ancestor for every single human alive on Earth, and, for Europeans at least, anyone who was alive and had children 1,000 years ago is the ancestor of every person of European descent alive today.
So it only takes a few dozen generations before analysis of our crossed-over, interbred nuclear genomes gets so messy that we’re tracing complex statistics instead of neat and tidy family trees. So to make it easier, instead of nuclear genomes, we often compare the tiny, circular genomes that persist within our mitochondria.
You’ll recall from biology class (you were paying attention, right?!) that our mitochondria used to be free-living bacteria, complete with circular, prokaryotic genomes. While most of that ancient genome has disappeared (or migrated to our own nuclear genome), our cellular energy factories still hold a circle of DNA that gets passed down to baby mitochondria when a cell divides and when a mommy and daddy lie down (or stand up, or whatever page of the Kama Sutra they’re on) and do Grown Up Stuff™. What’s weird is that (probably because eggs are big and sperm are small) every one of your mitochondria came from your mom, not your dad.
By comparing mitochondrial genomes from the past with mitochondrial genomes from around the world today, we are fairly certain that one single female of the Homo sapiens crew, living in Africa about 100,000-200,000 years ago, is the ancestor of every living human being today. We call her Mitochondrial Eve. She wasn’t the only human female alive then, and she wasn’t the only human with mitochondria. She’s just the one whose kids ended up covering the Earth.
Yeah, people whose recent ancestors come from South Asia look different from people whose recent ancestors come from Sweden. But that’s just human genetic variation, the same way that I have blonde hair and my friends Jamie and Eric are orange-haired gingers.
People have grouped together (and often excluded other groups) throughout history for a variety of reasons, some of them good, and many of them unthinkably horrible. Because of this, our ancestors often bred with those close to them in geography as well as culture, reinforcing bits of human genetic variation in traits like skin color and facial features. We invented “race”. Evolution just made different kinds of people.
All of this is a long way of saying that while your original question doesn’t have an answer, studying genetic differences based on geography and culture is still important to science. Not because it shows us how we are different, but because it highlights our human connections, and reminds us of our shared experience and common origin in a world that could always use a bit more of that kind of thinking.
Race: A scientific idea ready for retirement
I was reading through this year’s responses to the annual Edge question, What scientific idea is ready for retirement? and came across a gem of a response from Penn State’s Nina Jablonski regarding race.
It’s just so perfect, I’ve gratuitously excerpted practically all of it here:
The mid-twentieth century witnessed the continued proliferation of scientific treatises on race. By the 1960s, however, two factors contributed to the demise of the concept of biological races. One of these was the increased rate of study of the physical and genetic diversity human groups all over the world by large numbers of scientists. The second factor was the increasing influence of the civil rights movement in the United States and elsewhere. Before long, influential scientists denounced studies of race and races because races themselves could not be scientifically defined. Where scientists looked for sharp boundaries between groups, none could be found.
Despite major shifts in scientific thinking, the sibling concepts of human races and a color-based hierarchy of races remained firmly established in mainstream culture through the mid-twentieth century. The resulting racial stereotypes were potent and persistent, especially in the United States and South Africa, where subjugation and exploitation of dark-skinned labor had been the cornerstone of economic growth.
After its “scientific” demise, race remained as a name and concept, but gradually came to stand for something quite different. Today many people identify with the concept of being a member of one or another racial group, regardless of what science may say about the nature of race. The shared experiences of race create powerful social bonds. For many people, including many scholars, races cease to be biological categories and have become social groupings. The concept of race became a more confusing mélange as social categories of class and ethnicity. So race isn’t “just” a social construction, it is the real product of shared experience, and people choose to identify themselves by race.
Clinicians continue to map observed patterns of health and disease onto old racial concepts such as “White”, “Black” or “African American”, “Asian,” etc. Even after it has been shown that many diseases (adult-onset diabetes, alcoholism, high blood pressure, to name a few) show apparent racial patterns because people share similar environmental conditions, grouping by race are maintained. The use of racial self-categorization in epidemiological studies is defended and even encouraged. In most cases, race in medical studies is confounded with health disparities due to class, ethnic differences in social practices, and attitudes, all of which become meaningless when sufficient variables are taken into account.
Race’s latest makeover arises from genomics and mostly within biomedical contexts. The sanctified position of medical science in the popular consciousness gives the race concept renewed esteem. Racial realists marshal genomic evidence to support the hard biological reality of racial difference, while racial skeptics see no racial patterns. What is clear is that people are seeing what they want to see. They are constructing studies to provide the outcomes they expect. In 2012, Catherine Bliss argued cogently that race today is best considered a belief system that “produces consistencies in perception and practice at a particular social and historical moment”.
Race has a hold on history, but it no longer has a place in science. The sheer instability and potential for misinterpretation render race useless as a scientific concept. Inventing new vocabularies of human diversity and inequity won’t be easy, but is necessary.
Well put, I think. Read the rest here.
Bill Nye’s appearance on Dancing With The Stars is bad for science because it reinforces stereotypes against women and minorities …
That’s the thesis of Jennifer Welsh’s piece at Business Insider. I encourage you to read the whole thing before making a knee-jerk reaction to that statement, because she includes a lot of important data in her article that I agree with. It’s just that I don’t agree with her framing. Bill Nye is not the enemy here.
What do we mean when we say someone or something is a “negative stereotype”? The real danger there is not always the stereotype itself, but rather the stereotype threat, that a member of a group will self-reinforce the image implied by a stereotype. We know that this happens, and Welsh includes several good examples in her article. For instance, young girls do worse in math class when female teachers exhibit anxiety about the subject. Take away the “anxious math girl” image, and they perform equally with (or better than) boys. In essence, the risk is believing that because others view you as inadequate, you are in fact inadequate.
Yes, Bill Nye’s dance sequence on DWTS was nerdy. He played a bumbling, over-the-top character in a lab coat, equal parts comical and charming. In other words, he played Bill Nye, the same way that Bill Nye the person has always played “Bill Nye” the character. Why, when it worked so well as a teaching vehicle on The Bill Nye Show, does “Bill Nye” the character all of a sudden become a stereotype threat when he’s dancing in prime time?
Maybe it’s because he’s being played as the butt of a joke, like Welsh explains. Sure, he played into an old trope of “dork gets sexy person to like them and suddenly doesn’t look dorky anymore" (also seen in such films as She’s All That. She took off her glasses! She’s cool now!). But is that really the threat it’s made out to be? I think there’s a better case to be made that Bill Nye being on DWTS creates an image of a scientist as popular, likable and socially accepted, the very arc his dance routine followed. If we want to point fingers at media that uses awkward white nerds as the eternal butt of a joke in the supposed name of geek culture, look no further than The Big Bang Theory.
Bill Nye is an effective science teacher, one that I think genuinely made an impact for males, females, whites, POC, and others, because he spoke to his “students” as peers. That’s even in the mission statement for his show. His show was accessible to so many groups, I think thereby breaking down stereotype threats, not only because it spoke to its audience inclusively, but because it was truly accessible, as in you can watch this in every classroom in America with access to a TV. But maybe I can’t see past the good parts of Bill Nye the white guy scientist because I’m Joe Hanson the white guy scientist, and that’s a possibility I accept.
I think Welsh calls attention to an important issue, but sloppily. How we can change the public image of a scientist to affect the inclusion of women, POC and LGBTQ groups into the science sphere is some Serious Business™. See, yanking a dancing Bill Nye out of our hat shines the spotlight where it doesn’t need to be, obscuring the systemic problems that are truly at play here: How often-ill-prepared teachers interact with and encourage their students (or don’t), increasing access to quality science education across socioeconomic classes, removing social hurdles such as gender and race bias in faculty and entry-level hiring, providing same-sex benefits to university employees (like grad students and faculty) and erasing a woman’s seemingly-binary choice of starting a family or committing to a career in science, to name a few.
Maybe I’m just inclined to focus on the positive, to be optimistic about how a dancing Bill Nye can make a difference,or how Neil deGrasse Tyson will change the world in prime time next year. I think the problems that Welsh identifies are real, I just don’t think Nye’s the demon we’re looking for. Thoughts?
Melanie Tannenbaum writes over at SciAm about the psychology behind split-second decisions
like the one George Zimmerman made when he shot Trayvon Martin. George Zimmerman did not make a split-second decision, that was the wrong wording, and a bad lede into the study, which is about split-second reactions.
A 2002 study put college students in a similar situation and measured their ability to make snap judgements of whether to shoot:
Groups of college students were told that a series of people would come on the screen in front of them and would either be holding a gun or a neutral object, like a wallet, aluminum can, or cell phone. If the participants correctly shot an armed target, they would receive 10 points; if they correctly did not shoot an unarmed target, they would receive 5 points. Shooting an unarmed target deducted 20 points, and not shooting an armed target – the most potentially dangerous outcome for a real police officer on the streets – would result in the harshest penalty of all, a 40-point deduction.
As each target appeared on screen, participants had to decide as quickly as possible if the target was holding a gun or a harmless object, and subsequently whether to shoot or not shoot by pushing a “shoot” or “don’t shoot” button. Unbeknownst to participants, the researchers had manipulated one critical feature of the targets – some of the targets were White and some were Black.
You can probably guess what the results were, but the psychology might surprise you. It turns out that a person does not have to carry overt racist feelings to make a mistake in this situation. The results showed that merely being aware of racial prejudice spawned shooter bias, no matter if the shooter’s perspective on the prejudice was positive or negative.
By all indications, George Zimmerman is an overtly racist man, and that lies at the heart of this tragedy. But this study raises an important point: One does not have to be overtly racist to make the same mistake. Check out Melanie’s full post and see what you think.
Edit: Like I anticipated, some people aren’t getting the point of this article. George Zimmerman is a racist who murdered an unarmed black boy. This is a psychological study that says that the same thing can happen, in a simulation, without overt racism. This is not a defense of Zimmerman, because he is indefensible.
And They’re OFF!
As part of the World Cell Race at the American Society for Cell Biology meeting last week, teams from around the world raced cells in a petri dish to claim the title of “fastest cells in the world”.
I’m sure there’s some wonderful insights into cell motility here, but you probably just want to know who won … it was a bone marrow cell from Singapore, and it clocked in at 0.000000312 kilometers per hour.
Sperm cells were obviously disqualified.
The grant gap was quite substantial. Getting a grant is never easy, but in round numbers, white researchers succeeded about 25 percent of the time, and blacks succeeded about 15 percent of the time. An obvious question is whether this is the result of overt racism.
"We can’t rule it out, but that’s not what we think is happening," [Raynard] Kington says. "I think the more compelling case is that it is unconscious in various ways."
… "If indeed we are biased in the way that we review some of our applications, that means that the American people’s money may not be going to the strongest scientific ideas," he says.
Compare that to a graph of raw U.S. demographics (corrected for Hispanic ethnicity overlap) that I made based on 2010 census data:
Draw your own conclusions … what do you think?
This is not gonna raise any eyebrows, not at all. Certainly not a sensitive subject or anything. ;)
"Some may say it as a joke, others might find it offensive, but it turns out there’s some truth to the idea that people of other races “all look alike.” A new study demonstrates that people have more trouble recognizing faces of people of other races.