Monday, March 28, 2016

My Brother's Keeper

Photo by pugphai at
Relationships with siblings tend to be complicated. We love them, but they drive us nuts. We want to help them, but not if it takes too long or costs too much. These are common struggles because the psychology of these relationships is in our biological heritage.

Let’s play a thought experiment: Say a runaway trolley is heading down the tracks. Ahead of the trolley are five people tied to the tracks that are about to become mush (Don’t ask why they are tied up on the tracks – Just assume the evil boogeyman got them). You are in the distant train yard next to a lever. If you pull the lever, the trolley will switch to another set of tracks, sparing the lives of the five tied-up people. But… there is one person tied to the other set of tracks, so pulling the lever would also kill that one person. What do you do?

Photo by David Ingham at Wikimedia.

This is the classic scenario in a field of ethics called “trolleyology”. (Yes, this is a thing). If you are like 9 out of 10 people, you chose pretty quickly to kill the one person to save the five. Our utilitarian morals tend to value more lives over fewer.

But what if that one person is your daughter? Your mother? Your brother? The dilemma just became harder, didn’t it? Not because the one life is now inherently worth more than the five… but because that one life is worth more to you.

We are a social species that tends to live in family groups, as were our ancestors for over 100,000 generations. We also share more of our genes with our closest family members through shared inheritance. For example, we each share about half of our alleles (our particular version of a gene) with each of our biological parents. Our siblings with the same two parents have also inherited about half of each parent’s alleles, but not necessarily the same ones that we did. This means that we share about half of our alleles with our full-siblings too (and we share about a quarter of our alleles with our half-siblings). Following this same math, we share about a quarter of our alleles with our aunts and uncles and about an eighth of our alleles with our cousins. The more distant the relative, the fewer alleles we have in common.

Now let’s play another thought experiment: Say there is a population of animals where some individuals have lots of babies and raise their children to be good parents, and other individuals don’t have a lot of babies. An individual that has the “have lots of babies” and “be a good parent” alleles are going to share, on average, half of those alleles with each of their many children. They are also going to have more surviving children than most of the individuals that do not share those alleles. So, over many generations, more individuals in the population are going to have the alleles that make them have more babies and take care of them, right?

But there is another potential outcome to this thought experiment. Yes, we share about half of our alleles with our children, but we also share about half of our alleles with our full-siblings. Therefore, a “take care of your siblings” allele has the same probability of spreading through the population over generations as a “be a good parent” allele.

The genes that predispose our behaviors and decisions have been shaped by the generations of our ancestors that determined which of their relatives would have the support to raise more or fewer children… or none at all. In the 1960s, William Hamilton proposed a mathematical rule (called Hamilton’s Rule) for just such a decision:

rbB > rcC

where B is the number of individuals that survived because of you, rb is a measure of relatedness to those individuals, C is the number of individuals that died without your help, and rc is your relatedness to those individuals. This means that to pass on the most of our genes, we should factor in how many individuals and how closely-related they are to us when we decide who to help and who to sacrifice. 

For example, if you help to raise three of your siblings, each of which share ½ of their alleles with you and who would have died without you, but this means that you can’t take care of your own child that dies as a result, then this equation would be (½) X 3 > (½) X 1. This means that, mathematically, you should opt to raise your three siblings rather than your own child. J.B.S. Haldane, an influential geneticist, summed this decision process up when he was asked if he would give his life to save a drowning brother by responding “No, but I would to save two brothers or eight cousins”.

Inserting our close family members into the hypothetical trolley problem makes us squeamish because it puts the “take care of your family” alleles we have inherited in conflict with our utilitarian morals. We are literally the species we are today because we take care of our brothers and sisters as well as our children… even when they’re obnoxious.

Monday, March 21, 2016

Caught in My Web: Insights on Professional Conferences

Image by Luc Viatour at Wikimedia Commons.
We are approaching conference season. If you plan on attending a professional conference for the first time or for the umpteenth time, this edition of Caught in My Web should provide you with some helpful tips, strategies and stories.

1. Hilda Bastian at PLOS Blogs gives 7 tips for women at science conferences here (although these tips are good for everyone).

2. Jordan Gaines Lewis gives her personal insight from presenting her research at the 2016 AAAS Meeting at Gaines, on Brains.

3. On TEDBlog, Jedidah Isler reflects on this photo of herself with her colleague friends at the TED2015 conference.

An impressive group of professionals show each other mutual support at
this global conference about Technology, Entertainment and Design.
4. Felicity Muth blogs about her experience at the Animal Behavior Society Conference at her Scientific American Blog, Not bad science.

5. Before you present your research, consider these insights on the science of persuasion:

Monday, March 14, 2016

Can You Feel the Love Tonight? (A Guest Post)

By Maggie Nannenhorn

If you’re like me, you never truly realize how quiet winter is until all the sounds of spring come back in a chorus of celebration. Between the birds, crickets, and frogs, you can really hear the love in the air. So you can hear the love, but can you feel the love?

Wood frogs are known for their chorus of calls that sound like a duck laughing. Seriously, tell a duck a good knock-knock joke and that is what a male wood frog sounds like when trying to attract a mate. He makes the call by expanding his two vocal sacs, membranes of skin underneath the neck, forming a bubble-like appearance. When a female surfaces, drawn to the call, the male frog clasps onto her, causing her to lay her eggs. The male frog then externally fertilizes the eggs. This form of mating is termed amplexus. The use of the call in the reproduction ritual is well studied. However, it is possible the small ripple formed in the water from the expanding vocal sack is relaying information that influences the mating behavior of these frogs.

Male wood frog resting on the water surface. Image by Maggie Nannenhorn.
Male wood frog calling with vocal sac expanded.
Notice the ripple it creates in the water. Image by Maggie Nannenhorn.

In 2010, Gerlinde Höbel and Robb Kolodziej from the University of Wisconsin-Milwaukee conducted an experiment that explored the use of water surface waves in wood frog reproductive behavior. They hypothesized male wood frogs use ripples in the water to find female wood frogs to mate with, while female wood frogs use ripples in the water as indicators of harassing males.

Video of a wood frog calling by Maggie Nannenhorn.

Wood frogs have a very short mating period: only 1 to 3 days per year! This study occurred on April 1st - 2nd, which corresponded with the wood frogs’ natural mating period. The first component of the study was the observation of a pond containing more than 500 wood frogs in amplexus. Amplexus was determined by the presence of males clasping on to the backs of female frogs in the water. They learned males approach surface waves on the water and clasp onto the frog that caused the ripple. However, females move away from surface waves on the water and dive downward.

After preliminary observations, they developed an experiment to cause rippling of the water. The first experiment tested the effect of stimulation (dipping a wooden probe into the water) near male wood frogs. The males tested were randomly assigned to either a control group or an experimental group. The 34 males in the control group were simply observed, and the direction and pattern of movement was recorded. For the experimental group, a long wooden probe was dipped in and out of the water 25 cm away from a male frog for 10 seconds. The resulting ripple was meant to mimic a ripple caused by a female frog moving in the water. Based on the hypothesis, the male wood frogs should approach the ripple hoping to find a female to mate with. Of the 60 males in the experimental group, half were stimulated from the right and half were stimulated from the left. A circle diagram (depicted below) was used to map the direction the males moved.

Video of a wood frog approaching ripples by Gerlinde Höbel.

This figure shows: a) the control group and b) the experimental group.
A circle diagram representing the reproductively driven movement direction
of wood frogs (Lithobates sylvaticus) in a laboratory pool as a result of
stimulated surface waves on both the left and right sides.
Figure from: Höbel, G., & Kolodziej, R. C. (2013). Behaviour, 150(5), 471-483.

The females are difficult to observe in the field since they prefer to stay beneath the surface. So, the researchers set up a tank to test 4 breeding pairs of wood frogs. They tested the females both while in amplexus and while alone. They dipped wooden probes into the water to stimulate the females on both the left and the right side in turn. Their positions and directions were also recorded using a circle diagram.

So, what did they find? It turns out, their predictions were correct! The males would approach the ripple caused by the probing. This is likely because the ripple may indicate a competing male they want to drive away or a female they want to mate with. The females moved away from the ripples by either swimming away or diving underneath the water surface. This may reduce the amount of harassment they receive from males. If a female becomes the center of attention for too many males, she may drown from the weight of them all attempting to grab her. Besides, if a male is fit, he will likely be able to catch up to her and successfully mate with her despite her swimming away.

The mating calls and movement of the wood frogs affect the surface waves, and these waves are used to make sexual behavior choices. This spring, the chorus of love will still ring out through the reeds, and I encourage you to take a moment to stop and listen. When you’re stopped, take a moment to notice the waves of love bringing these wood frogs together. Hopefully this spring, we will all be feeling the love.


Höbel, G., & Kolodziej, R. (2013). Wood frogs (Lithobates sylvaticus) use water surface waves in their reproductive behaviour Behaviour, 1-13 DOI: 10.1163/1568539X-00003062

Monday, March 7, 2016

Science Beat: Round 6

It is that time in the semester when midterm pressures start building and the facts we're supposed to be learning for tests start disappearing like lost keys. Sometimes putting the material in a new context can help. Try these:

Cellular Biology:

Anatomy and Physiology:

Cellular Respiration:

Vote for your favorite in the comments section below and check out other science songs worth learning at Science Beat, Science Beat: Round 2, Science Beat: Round 3, Science Beat: Round 4, Science Beat: Round 5, and Science Song Playlist. Check out some song battles about the life of scientists at The Science Life, Scientist Swagger and Battle of The Grad Programs! And if you feel so inspired, make a video of your own, upload it on YouTube and send me a link to include in a future battle!