Honoring Billie J. Swalla's Legacy with a Lifetime Achievement Award

11/14/2025

When Billie Swalla learned of her nomination for the Developmental Biology-Society for Developmental Biology Lifetime Achievement Award, she felt "humbled to be among Nobel Prize-winning colleagues," never imagining she would be counted among their ranks. But to the scientific community, and especially to her nominators, this recognition felt long overdue.

With over 100 publications, more than four decades of pioneering research, and a legacy as both mentor and leader, Swalla has helped transform the evolutionary developmental biology (evo-devo) community—one discovery and one mentee at a time. Her story is not only one of scientific accomplishment, but also of perseverance, boldness, and unwavering support for the next generation of scientists.

Trailblazer: Stepping Forward So Others Could Follow

Swalla recalled a visit from her brother to her current home in Friday Harbor in the San Juan Islands. As they watched whales glide across the horizon, he turned to her and asked, "Aren't you from the same family I am?" She smiled and replied, "Yes, but I took a different path." In fact, she was the first in her family to pursue higher education.

As a graduate student, Swalla studied developmental ecology and evolution, eventually falling in love with embryology under the mentorship of William R. Jeffery. One of the most formative experiences of her early career was attending the renowned Embryology Course at the Marine Biological Laboratory in Woods Hole—a pivotal moment that helped shape her future research.

That opportunity, however, came with institutional and cultural barriers. At the time, Woods Hole did not offer family accommodations, forcing many participants, especially mothers—to make the painful choice of leaving their families behind for the summer. It reflected a scientific world largely built for men with the time and resources to pursue research full-time, often supported by the unpaid labor of a wife or caregiver, which allowed them to be away from home for extended periods.

Swalla and her son, Tony, at the Marine Biological Laboratory in Woods Hole, Massachusetts in 1983.

This marked one of Swalla's earliest efforts to challenge those norms. As a single mother, she was resolute. She refused to attend the course unless she could bring her young son with her. In response, the program made an exception, ultimately setting a new precedent for other parents and non-traditional students striving to balance family and professional advancement. In her boldness, she helped open the door to greater equity in this small corner of science.

Later challenges were met with a similarly persevering attitude. "I had to push through personal challenges to keep moving forward," Swalla shared. "But I never wanted to give up science. It was the thing that gave me the most fulfillment."

Radical: A Bold Idea Backed by Rigorous Science

"Billie's disciplined attitude, rigorous lab routine, and tenacity in her daily research have positioned her as a leader in the evo-devo community."

— Federico Brown, former graduate student and mentee

Swalla studies the evolution of the chordates, the phylum that includes tunicates and vertebrates. Before her studies, the field was dominated by conflicting theories: Garstang’s hypothesis that vertebrates evolved from the motile larvae of echinoderms by the retention of larval-like traits in adult forms, versus Romer’s hypothesis that they evolved from a colonial hemichordate ancestor through the gradual acquisition of adaptations for increased motility. Swalla’s work brought a molecular genetic approach to chordate evolution, particularly the tunicates and hemichordates, which helped to clarify a likely worm-like deuterostome ancestor.

Swalla is best known for her work on sea squirts—a type of tunicate that has been critical to understanding the evolution of vertebrates. Fascinatingly, ascidians’ larval form displays a hollow notochord and tail, just like their vertebrate relatives. These homologous structures suggested to Swalla that the gene regulatory networks for notochord and muscle are conserved within the chordates, and many labs have since shown the conservation of the gene regulatory networks for notochord and muscle across the chordates.

Larval vs adult morphology of the solitary Molgula ascidian species Swalla studies. A) Tailed larva of the Molgula oculate. C) Tailless sister-species Molgula occulta. B) The hybrid larval resulting from spawning tailed and tailless species together. Note the intermediate short tail and small eye spot. A’ and B’) The unassuming adult forms of the two Molgula ascidian sister species. The mature ascidians form a protective crust of sand around their bodies except their siphons [marked by a star] which leaves it clear for feeding and expelling waste. A’) Adult Molgula oculate. B’) Molgula occulta.

Swalla’s early postdoctoral work began on two species of ascidians with similar adult forms, but distinct larval forms. These were the tailed larval (Molgula oculate) and its tailless larval sister-species (Molgula occulta) collected off the coast of Roscoff, France (see figure). Both species share the same sessile adult form, appearing like inconspicuous marine rocks. But as larvae, the tailed ascidian is more motile and therefore can have a longer juvenile period. The tailless species, in contrast, is largely immobile and undergoes a rapid metamorphosis into its tougher adult form for protection. Swalla’s research lab discovered that in the tailless ascidians, many of the larval genes that control tail development have mutations that make them non-functional. She tested this discovery by crossing the two species, generating a hybrid that has an intermediate short-tail phenotype. This tailed and tailless ascidian system was studied by renowned developmental biologist Norman John (N.J.) Berrill, one of Swalla's research heroes, and he admitted in a handwritten letter that he had never thought about hybridizing the two species and that he was delighted that work was continuing to be done on the system.

Swalla spent the next decade exploring the molecular and genetic underpinnings of another vertebrate-like feature of ascidians: the gill slits. She showed that Pax1/9, a gene crucial to gill slit development, is conserved across ascidians and their sister groups. It was already known that when knocked out in vertebrates, the animals fail to develop their vestigial gill slit structures. Her phylogenetic work mapped homologous gene sequences across species, constructing gene trees and showing similarities and differences in gene expression in the Deuterostomes. Together, her work pointed to shared ancestral mechanisms for making gill slits, notochords, and tails in all chordate relatives. Her selection for the Lifetime Achievement Award is a recognition not just of years of dedicated research, but of scientific courage—the willingness to study evolution and development – and encouraging others in the field along the way.

This unabashed approach has inspired countless junior scientists to voice bold ideas and pursue questions that push the field in new directions. As Fernanda X. Oyarzún, Swalla's former mentee, research scientist, and visual artist, reflects: "I also observed that her outgoing personality and unapologetic willingness to voice opinions grounded in evidence … sometimes made others uncomfortable. This discomfort …was a reflection of broader societal unease with intelligent women who refuse to apologize for their original ideas or for challenging the status quo."

Pillar: A Firm Advocate and Compassionate Mentor

But Swalla is more than a scientific authority—she is a deeply human presence. A devoted mentor, she has trained a generation of scientists, many of whom have gone on to lead their own research programs around the world. In a moving tribute, former mentee Brock Roberts wrote: "She found the spirit that lived in me … Billie taught me to work hard and also to recognize the doing of science as a privilege and something capable of great fulfillment."

Her mentorship has never been just about experiments or publications—it has been about helping others find their voice, their purpose, and their confidence in science. Throughout her career, Swalla has worked relentlessly to advance equity. As President of both the Society for Integrative and Comparative Biology and the Pan-American Society for Evolutionary Developmental Biology, she championed inclusion of diverse scientific topics at conferences. Brown adds: "As President, Swalla focused on raising awareness of inclusion both in diversity (i.e., gender balance and minority representation) and in scientific representation at the meetings."

Swalla also served nearly a decade as Director of Friday Harbor Laboratories, one of the world's leading marine research centers. During her leadership, she expanded educational and research programs, reinforcing the institution's status as a global hub for marine and developmental biology. The transformation of Friday Harbor Labs under Swalla's leadership has influenced generations of scientists.

Despite her high standards and rigor, colleagues often describe Swalla as full of warmth and laughter. She embodies the spirit of mentorship and collaboration—offering her time, energy, and compassion to help others thrive, even while balancing her own research, leadership, and motherhood. Roberts recalls his time as a grad student: "She had so much personality, made me laugh so frequently, and allowed me to make her laugh—or at least laugh at my attempt at it … Yet there was another dimension to Billie: a huge heart, voluminous and frequent laugh, a cross look in her eyes when something irritated and … [simultaneously] amused her.”

Trailblazer, Radical, Community Pillar

Though the Lifetime Achievement Award recognizes past accomplishments, Swalla remains an active and engaged member of the developmental biology community. She is currently working on exciting new research related to ascidian evolution and continues to mentor junior scientists. If she had unlimited resources, she says, she would fund international fieldwork and postdocs to further explore chordate evolution—and travel the world correcting museums' outdated displays of vertebrate origins.

For Swalla, science is more than a career—it's a calling. One rooted in curiosity, shaped by resilience, and carried forward through her mentorship. "Her career embodies the spirit of curiosity, innovation, and dedication that this award seeks to honor," wrote Alexandre Stolfi, one of her former mentees.

In every sense, Swalla exemplifies what it means to devote one's life to discovery—and to leave the field better than she found it. As her colleagues, mentees, and peers can attest, her impact is lasting, her work transformative, and her legacy still in the making.

Last Updated 11/14/2025