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Some dogs love to play fetch, while others watch the tennis ball roll by with little interest. Some run circles around their owners, herding them, during walks, while others stop to sniff everything in their path.

It begs the question — why do dogs behave so differently, even within their own breeds?

Erin Hecht, assistant professor of human evolutionary biology at Harvard, is seeking answers through The Canine Brains Project, part of the University’s Brain Science Initiative. She recently gave a talk on the emerging field of canine neuroscience, and what we know so far about our furry friends.

Dogs, according to Hecht, have the potential to teach us a lot about brain development, having been domesticated roughly 20,000 to 40,000 years ago — a blip on the evolutionary timeline. For context, modern humans emerged roughly 300,000 years ago. Because domestication was relatively recent, modern dog breeds live alongside ancient breeds, making comparison possible.

“Darwin saw dogs as a window on mechanisms of evolution,” Hecht said. “When we’re looking at dogs, as a natural experiment and brain behavior evolution all we have to do is look at their brains and see what evolution did in order to satisfy those selection requirements.”

Hecht’s lab performs MRI scans on nearly 100 canine brains a year and conducts owner surveys looking at dogs’ working skills, like hunting, herding, and guarding, compared to skull shape, body size, and breed.

The lab looks at domesticated breeds like Great Danes or other hunting dogs or designer dogs — a practice that took really took hold during the Victorian era — as well as ancient dogs like huskies and “village dogs.”

“About 80 percent of the dogs living on the planet today are what’s known as village dogs. These are free-ranging animals that live as human commensals. So they’re living within human society, but they’re not pets,” Hecht said.

Some initial findings from the lab include the discovery of neurological differences in dog breeds, including that premodern dogs on a whole have larger amygdala — the part of the brain that controls emotional processing and memory. Such heightened environmental-monitoring skills would come in handy for dogs deciding which humans to steal scraps from and which to avoid.

Modern dogs have a bigger neocortex — the part of the brain that controls motor function, perception, and reasoning. It may play a part in modern dogs’ increased behavioral flexibility, or ability to adapt to new environments.

Hecht’s lab connects personality and skill differences in dogs to six different parts of the brain: the regions controlling drive and reward; olfaction and taste; spatial navigation; social communication and coordination; fight or flight; and olfaction and vision. While breeds we see in our homes today share similarities in these pathways, Hecht’s research suggests the traits can be attributed more to selective breeding than ancestral DNA.

“There has been very strong recent specific selection in individual breeds rather than founding effects in ancestral founding populations,” Hecht said. “So then we can look at behavior and ask whether the types of behaviors that different lineages have been selected for historically … [explain] each dog’s anatomy and these six brain networks. And it seems like there are some interesting relationships here.”

More than breed itself, pathways are impacted by a dog’s head shape and size. For example, Hecht’s lab has found that bigger dogs have larger neocortices than their smaller counterparts, and therefore generally are more trainable and less anxious. Dogs bred for their narrow skulls may see that impact their behavior.

“It stands to reason that if you’re manipulating the shape of a skull, you’re going to be manipulating the shape of the brain,” Hecht said. “But this confirms that dogs with these extreme skull morphotypes have impacts on their brain anatomy that likely affects behavior.”

In conjunction with the MRI scanning, Hecht’s lab measures dogs’ behavior with an assessment called C-BARQ, the Canine Behavioral Assessment and Research Questionnaire. The survey, which is filled out by the dog’s owner, assesses behaviors such as aggression, trainability, and rivalry, to name a few.

“There was one study that collected C-BARQ data on 32,000 dogs from 82 different breeds and then performed clustering on the survey responses. And the data clustered more on the body height of the dogs than on breed relatedness. So size was a better predictor than breed in predicting temperament scores on this C-BARQ assessment,” Hecht said.

She added that just because certain dogs have brain makeups that suggest a certain disposition, it doesn’t lock them into those behaviors. That goes especially for working skills.

“Training is almost always necessary. I have yet to hear of any particular breed of working dog, where it’s just born knowing how to do its job,” Hecht said.

But whether you have a pit bull that acts like a chihuahua or a Yorkie that likes to run with the big dogs, a look inside their brain might help explain why they are the way they are.

Find out more about the work happening in the Hecht lab or see if your dog is a study candidate.

Humans have been considered unique for their ability to form relationships for mutual benefit not just within immediate kin groups but across and between them, even with total strangers.

It turns out that one of our closest living relatives, bonobos, are also able to think outside the group.

These were the findings of a Harvard study that involved two years of data collection in the deep forests of the Democratic Republic of Congo, where up to 20,000 of the endangered apes make their only home. The ability to engage in such “out-group” cooperation is the foundation on which humans have created societies and cultures through trade and knowledge-sharing.

“Our work with bonobos is showing that cooperation beyond social borders, without immediate payoff between unrelated individuals, is not uniquely human,” said senior author Martin Surbeck, assistant professor in the Department of Human Evolutionary Biology, who has researched bonobos for 20 years. The study was published in Science with lead author Liran Samuni, a former Harvard research associate who works at the German Primate Center in Göttingen.

A previous study, based on the same bonobo communities, found that the primates maintained distinct, stable social borders, so called “communities.” In their latest analysis, Samuni and Surbeck found evidence of cooperation between members of different communities, facilitated by an assortment of key individuals. These certain few consistently engaged in behaviors such as grooming and food-sharing and acted as links between groups — think ape ambassadors. Within each behavior, individuals cooperated with specific counterparts who were also good cooperators in that domain.

When animals of two different species mate, their hybrid offspring can be unhealthy or sterile. Often, only one sex is affected.

Sexual differences in fertility follow a pattern known as Haldane’s Rule, which states that hybrids are afflicted more when they inherit two different sex chromosomes. In mammals, males have XY sex chromosomes, so male “ligers” and “tigons” (offspring between tigers and lions) are sterile, while females, which have two X chromosomes, tend to be more fertile. But in butterflies as well as birds, females have ZW sex chromosomes while males have ZZ, so according to Haldane’s Rule, it is females that are sterile.

What insights could this natural phenomenon hold for speciation, the process in which different biological lineages split? James Mallet, professor of organismic and evolutionary biology in residence and associate of population genetics in the Museum of Comparative Zoology, and senior author of a new study in Proceedings of the National Academy of Sciences, takes a stab at the “why” behind Haldane’s Rule, using butterfly genetics as a guide.

Designed and led by former graduate student Tianzhu Xiong, the study investigated hybrid sterility in butterflies, creating hybrid crosses of different species to determine which particular genes were responsible for the phenotype.

According to analysis by Xiong, now a postdoctoral researcher at Cornell, the sterility trait in hybrid butterflies is probably tied to many genes scattered across the Z chromosome. Thus understanding all the genetic mechanisms behind it will require further study.

For the research, Xiong and colleagues created hybrids of Papilio swallowtail butterflies. They found that problems associated with hybrids, such as low pupal weight and ovary malformation in the females, happened because of uneven mixing, or “introgression,” between the Z sex chromosome and all the other chromosomes. This observation points to many genes working together to produce a balance within each species.

The balance between the Z chromosome and the rest of the chromosomes is disturbed when the former is inherited from only one species, as in female ZW hybrids. The W chromosome characteristic of female butterflies carries very few genes and is not involved. Furthermore, Xiong showed that female hybrids of another butterfly, Heliconius, studied by Neil Rosser and colleagues, also followed the same multigene pattern on the Z chromosome.

“Initially, I was in a mindset of hoping to find a major gene that causes the phenotype,” Xiong said. “But it turns out that the answer is more mathematical than expected, and that a very large number of genes actually explain the pattern better.”

The analysis shows that hybrid sterility may be like height in humans — polygenic, or involving multiple genes. “Tianzhu has shown it is the fraction of the Z chromosome that matters, not whether you’ve got a particular problem on one region of the chromosome,” Mallet said.

The work was supported in part by the National Science Foundation.

The warming climate is having ripple effects across ecosystems, including plants, which have evolved clever mechanisms to conserve water when stressed by drought.

But are plants likelier to defend themselves against dry air or dry soil? This question is hotly debated among climate scientists, and the distinction matters: While there’s consensus on the trajectory of temperature rise over coming decades, less is known about how global warming will affect soil moisture. Understanding this dynamic may help decide the most effective ways to ensure the survival of robust plant life.

A team led by Kaighin McColl, assistant professor in the Department of Earth and Planetary Sciences and the John A. Paulson School of Engineering and Applied Sciences, have new research in Nature Water indicating that plant drought-defense mechanisms, which involve closing tiny pores on leaves called stomata to limit photosynthesis and conserve water, are more likely triggered by dry soil than by dry air.

Their results challenge recently held views and were derived from a place with no plants at all — the barren salt flats of Utah and Nevada.

Previous research had found that plants are likelier to have closed stomata in the presence of dry air, rather than dry soils, so it was assumed that aridity triggered the drought response. But McColl and colleagues suspected these results did not tell the whole story about plant vulnerability to drier environments.

“The problem with this argument is that correlation does not imply causation; when plants close their stomata, that could actually be causing the air to get drier, rather than the other way around,” McColl said.

To investigate their opposing hypothesis, McColl and lead author Lucas Vargas Zeppetello, a Harvard postdoctoral researcher who starts at the University of California, Berkeley, in January, used as their natural laboratory one of the only places on Earth that has a vigorous water cycle but doesn’t grow any plants — salt flats in the Western U.S. desert.

Using salt flats data provided by collaborators in Nevada and Utah, the researchers reproduced other researchers’ studies that had calculated the relationship between air dryness and moisture flux, or movement (in this case through evaporation), from the land surface and had attributed those values to plants closing their stomata to conserve water. The Harvard team found their calculations lined up almost perfectly with those previous studies, but with no plants in the salt flats, they knew there had to be another explanation.

In that plant-free environment, evaporation responds only to soil dryness. McColl and Vargas Zeppetello concluded that plant responses to lack of humidity may have been exaggerated in previous studies. They think instead that plants respond most acutely to dry soil, an environmental stressor that is known to reduce transpiration and photosynthesis.

What does this mean? Soil dryness matters more than air dryness when it comes to global plant ecosystems.

“Our findings put emphasis on projections for water in the future,” Vargas Zeppetello said. “People talk about consensus on climate change, but that really has to do with global temperatures. There’s much less of a consensus on what regional changes to the water cycle are going to look like.”

The research was supported in part by the National Science Foundation.

Nobel Prize-winning astrophysicist Kip Thorne has spent his career describing, through mathematics, some of the deepest mysteries of the universe. His latest project takes on similar material, but through poetry and paintings.

A nearly two-decade collaboration with artist Lia Halloran has extracted from Thorne’s brain the pictures that accompany those highly technical descriptions and brought them to life in their new book, “The Warped Side of the Universe: An Odyssey Through Black Holes, Wormholes, Time Travel, and Gravitational Waves.” The weighty tome blends complex science with whimsical art and features more than 300 ink-on-film paintings by Halloran alongside poetry by Thorne.

Thorne, the 2017 Nobel laureate in physics and emeritus theoretical physics professor at the California Institute of Technology, and Halloran, associate professor at Chapman University, shared the story behind their partnership at a Harvard Science Book Talk last week, moderated by MIT physicist and humanities Professor Alan Lightman (one of Thorne’s former students at CalTech).

The book, said Thorne, is not meant to teach the particulars of astrophysical concepts, but rather to “convey the essence of the ideas, the feeling, the experience of the ideas, without going into the technical details — like I do in my other life.”

It took an ailing screech owl to teach a scientist the value of up-close-and-personal study.

In a talk Monday at the Science Center, Carl Safina, an ecologist at Stony Brook University and author of several books about humanity’s relationship with nature, recalled that the chick was found on a friend’s lawn as the pandemic was tightening its grip on the world. In the picture Safina received, the bird looked beyond saving.

“How did it die?” he asked.

“It was just a downy little, dying thing,” Safina, whose most recent book is “Alfie and Me: What Owls Know, What Humans Believe,” said in his Harvard talk, which was sponsored by the FAS Division of Science, Harvard Library, and the Harvard Book Store and included questions from Clemson University ecologist Joseph Drew Lanham.

Safina and his wife, Patricia, took in the little bird of prey. They planned to nurse it back to health and then perform a “soft release,” in which the animal is set loose but stays nearby, supported with food while it learns the ropes of wild bird life.

But the owlet’s flight feathers didn’t grow in properly, leaving it grounded for months after it should have fledged. Safina delayed the release further to ensure the bird would properly molt — critical to renew feathers that keep birds warm and enable flight. Over those extended months, Safina got to know Alfie in ways that moved and changed him and his wife.

“An owl found me and then I was watching ‘an’ owl,” he said. “It was no longer an owl after a while, it was ‘she,’ because she had a history with us. … This little owl, who was with us much longer than we thought she would be, became an individual to us by that history and all those interactions.”

The bond with Alfie strengthened to the point that, when she was finally released, she created a territory with Safina’s Long Island home at its center. Safina was able to spend hours each day observing her in the woods as she learned to take care of herself in the wild, meet two mates, and raise chicks of her own.

When he heard Alfie calling, Safina said, he’d call back and she’d land nearby. Their closeness allowed him to learn more things about screech owls than is generally known. Field guides, for example, describe two known calls but he identified six, some of which you have to be quite close to hear. The relationship also opened a window for Safina onto personality differences between Alfie and her mates.

Lanham pointed out that Safina’s approach to Alfie — including the act of naming her — ran counter to widespread scientific practice. Safina said he wasn’t concerned about violating convention, particularly if something interesting like individual personality differences among owls could be learned.

“I’m interested in knowing what really exists, which is the basic purpose of science,” Safina said, adding that field research has documented personality differences among individuals of species from chimpanzees to elephants to wolves. “Every time they look for it, they find it.”

In the end, the experience caused Safina to ponder more deeply the differences between humankind’s relationship with nature writ large versus the kind of personal connection he was able to feel with a wild individual.

“What I learned from Alfie is that all sentient beings seek a feeling of well-being and freedom of movement,” Safina said. “That’s a guide to what’s right and what’s wrong to me.”