by Joshua Brown
University of Vermont Communications
Similar spanish version
AI-designed (C-shaped) organisms
push loose stem cells (white) into piles
as they move through their environment.
Credit: Douglas Blackiston and Sam Kriegman
new form of
To persist, life must
reproduce. Over billions of years, organisms have evolved many ways
of replicating, from budding plants to sexual animals to invading
Now scientists at the University of Vermont, Tufts
University, and the Wyss Institute for Biologically Inspired
Engineering at Harvard University have discovered an entirely
new form of biological reproduction - and applied their discovery to
create the first-ever,
The same team that
built the first living robots ("Xenobots,"
assembled from frog cells - reported in 2020) has discovered
that these computer-designed and hand-assembled organisms can swim
out into their tiny dish, find single cells, gather hundreds of them
together, and assemble "baby" Xenobots inside their
Pac-Man-shaped "mouth" - that, a few days later, become new
Xenobots that look and move just like themselves.
And then these new
Xenobots can go out, find cells, and build copies of
themselves... again and again...
"With the right
design - they will spontaneously self-replicate," says Joshua
Bongard, Ph.D., a computer scientist and robotics expert at
the University of Vermont who co-led the new research.
The results of the
new research (Kinematic
Self-Replication in Reconfigurable Organisms) were
published November 29, 2021, in the
Proceedings of the National Academy of
Into the Unknown
move around their
they collect loose
stem cells in their "mouths"
that, over time,
aggregate to create "offspring" Xenobots
that develop to look
just like their creators.
Blackiston and Sam Kriegman
In a Xenopus
laevis frog, these embryonic cells would develop into skin.
"They would be
sitting on the outside of a tadpole, keeping out pathogens and
redistributing mucus," says
Michael Levin, Ph.D., a professor of biology and
director of the Allen Discovery Center at Tufts University and
co-leader of the new research.
putting them into a novel context. We're giving them a chance to
reimagine their multicellularity."
Levin is also an
Associate Faculty member at the Wyss Institute.
And what they
imagine is something far different than skin.
thought for quite a long time that we've worked out all the ways
that life can reproduce or replicate. But this is something
that's never been observed before,"
co-author Douglas Blackiston, Ph.D., the senior scientist at
Tufts University and the Wyss Institute who assembled the
Xenobot "parents" and developed the biological portion of the new
profound," says Levin.
have the genome of a frog, but, freed from becoming tadpoles,
they use their collective intelligence, a plasticity, to do
experiments, the scientists were amazed that Xenobots could
be designed to achieve simple tasks.
Now they are
stunned that these biological objects - a computer-designed
collection of cells - will spontaneously replicate.
"We have the
full, unaltered frog genome," says Levin, "but it gave no hint
that these cells can work together on this new task," of
gathering and then compressing separated cells into working
"These are frog
cells replicating in a way that is very different from how frogs
No animal or
plant known to science replicates in this way,"
Sam Kriegman, Ph.D., the lead author on the new study, who
completed his Ph.D. in Bongard's lab at UVM and is now a
post-doctoral researcher at Tuft's Allen Center and Harvard
University's Wyss Institute for Biologically Inspired Engineering.
On its own, the
Xenobot parent, made of some 3,000 cells, forms a sphere.
"These can make
children but then the system normally dies out after that. It's
very hard, actually, to get the system to keep reproducing,"
But with an
artificial intelligence program working on the
Deep Green supercomputer cluster at
Advanced Computing Core, an evolutionary algorithm
was able to test billions of body shapes in simulation - triangles,
squares, pyramids, starfish - to find ones that allowed the cells to
be more effective at the motion-based "kinematic" replication
reported in the new research.
"We asked the
supercomputer at UVM to figure out how to adjust the shape of
the initial parents, and the AI came up with some strange
designs after months of chugging away, including one that
resembled Pac-Man," says Kriegman.
It looks very
simple, but it's not something a human engineer would come up
with. Why one tiny mouth? Why not five? We sent the results to
Doug and he built these
Pac-Man-shaped parent Xenobots.
parents built children, who built grandchildren, who built
great-grandchildren, who built great-great-grandchildren."
In other words, the
right design greatly extended the number of generations.
"parent" organism (C shape; red)
beside stem cells
that have been compressed
into a ball
Blackiston and Sam Kriegman
replication is well-known at the level of molecules - but it has
never been observed before at the scale of whole cells or organisms.
discovered that there is this previously unknown space within
organisms, or living systems, and it's a vast space," says
"How do we then
go about exploring that space?
Xenobots that walk. We found Xenobots that swim. And now, in
this study, we've found Xenobots that kinematically replicate.
What else is
Or, as the
scientists write in the Proceedings of the National Academy of
surprising behaviors just below the surface, waiting to be
Responding to Risk
Some people may
find this exhilarating.
react with concern, or even terror, to the notion of a
For the team of
scientists, the goal is deeper understanding.
"We are working
to understand this property: replication.
The world and
technologies are rapidly changing. It's important, for society
as a whole, that we study and understand how this works," says
millimeter-sized living machines, entirely contained in a
laboratory, easily extinguished, and vetted by federal, state and
institutional ethics experts,
"are not what
keep me awake at night.
risk is the next pandemic; accelerating ecosystem damage from
pollution; intensifying threats from climate change," says UVM's
"This is an
ideal system in which to study self-replicating systems. We have
a moral imperative to understand the conditions under which we
can control it, direct it, douse it, exaggerate it."
Bongard points to
the COVID 'epidemic'
and the hunt for a vaccine.
"The speed at
which we can produce solutions matters deeply.
If we can
develop technologies, learning from Xenobots, where we can
'We need a
biological tool that does X and Y and suppresses Z,'
could be very beneficial.
takes an exceedingly long time."
The team aims to
accelerate how quickly people can go from identifying a problem
to generating solutions,
living machines to pull microplastics out of waterways or build
new medicines," Bongard says.
"We need to
create technological solutions that grow at the same rate as the
challenges we face," Bongard says.
And the team sees
promise in the research for advancements toward regenerative
"If we knew how
to tell collections of cells to do what we wanted them to do,
ultimately, that's regenerative medicine - that's the solution
to traumatic injury, birth defects, cancer, and aging," says
"All of these
different problems are here because we don't know how to predict
and control what groups of cells are going to build.
Xenobots are a
new platform for teaching us."
that can Reproduce
scientists behind the Xenobots
participated in a
live panel discussion on December 1, 2021
the latest developments in their research.
Wyss Institute at Harvard University