Category Archives: Science

Virtual Reality for Bees

Virtual Reality(VR)  has always been, at bottom, an applied psychology experiment.  Intercepting sensory inputs and replacing them with synthetic input, and seeing just how “real” the experience can be requires an end-to-end understanding of just how senses work and sensory data is processed—deep problems of psychological science.

Of course, Homo (“let’s talk about me”) sapiens was first interested in monkeying about with human experience.  But these days Virtual Reality has been explored for other species including flies, mice, fish, and bacteria (!).  These studies are interesting because they demand that we take a subjects eye view, trying to understand what non-humans actually sense about the world.  (This kind of decentration is not the strong suit of our species.)

This winter researchers from Berlin report on work that  combines two of my favorite topics, VR and bees [1].   The VR was not intended to entertain the bees, it was to let them move as naturally as possible while being monitored.  The subject bees were placed on a tiny VR treadmill, surrounded by a miniature conical CAVE that presents “realistic” visual stimuli, coordinated with the bee’s movement.

The goal was to examine how bees learn.  The virtual environment was designed to represent a maze, a classic, if not beloved, experimental task.  Bees, unlike rats, are difficult to run through physical maze.  (If rats could fly, they’d never put up with mazes, either!)  In addition, the goal is to measure neural activity during the operant learning, which ain’t easy unless you can keep the subject in one place.

So the VR is used to move the visual world around the bee as it walks on the treadmill.  The bee stays in place hooked up to electrodes, and the digital scenery rolls by.

Several standard conditions demonstrated that the bees learned to associate colors and odors with rewards. The neural studies showed that different areas fired in response to the rewarded or non-rewarded target color. This confirmed that the same “mushroom body” area is modified by this operant conditioning and in earlier studies of classical conditioning, and for visual as well as odor stimuli.  (It would be shocking if this were not true!)

The study was limited by the classic philosophical conundrum of operant learning:  the theory postulates a temporal sequence of presumed neural activity. In principle, the brain responds to neural activity signaling the stimuli, “decides” to approach or avoid the stimuli, and triggers motor signals.

However, it is very difficult to pinpoint this “decision” point, and the clever VR and neural recordings did not make it possible.

“In the search for neural correlates of operant learning, one would like to analyze the point of decision where the animal initiates a walk toward one of the two colors. Unfortunately, such decision points were not obvious since every walking trajectory included several turns or stops making it impossible to isolate attempts to walk toward the color” ([1], p.17)

This study definitely showed neural plasticity directly correlated to sensory experience.  Unfortunately, there is little known about the actual role of the observed neural activity in behavior.  It is important to keep in mind that these are relatively coarse grained measurements, and that the actual mechanism of both the changes (the correlates of learning) and how the firing influences other parts of the brain (the presumed recall and decision making).  For that matter, we don’t even know for sure if the neural activity seen is primary (i.e., the site of the learning) or some kind of secondary side-effect (e.g., routing of signals from elsewhere).

Using VR does seem to give a cleaner experimental environment for this kind of study. But it does not magically solve all the hard problems of actually understand a bee’s brain.


  1. Hanna Zwaka, Ruth Bartels, Sophie Lehfeldt, Meida Jusyte, Sören Hantke, Simon Menzel, Jacob Gora, Rafael Alberdi, and Randolf Menzel, Learning and Its Neural Correlates in a Virtual Environment for Honeybees. Frontiers in Behavioral Neuroscience, 12:279, 2019. https://www.frontiersin.org/article/10.3389/fnbeh.2018.00279

Lithium Mines Seen From Space

Where does Lithium come from?

I have known about the light metal element Lithium for decades as the mysteriously effective anti-depressant  which has led to synthetic analogs. In this role, Lithium has saved countless lives, even if we have only the sketchiest idea of why it works.

But in recent decades, most of us have been carrying Lithium in our pockets and bags, in the form of nearly ubiquitous Lithium ion batteries. In this case, we do know how it works, and we also have learned just how exciting Lithium can be when it meets water.  Boom!  If mobile devices weren’t so darned necessary to modern life, we’d never allow such crazily dangerous technology in our homes.

But where do we get Lithium from?

As it happens, there is one main source, in the fittingly exotic high desert of the Atacama.  This area is one of the most remote and hostile places on the planet, home to many important astronomical observatories, and the home of flamingos, alpacas, and other rare animals.

In places there are mineral sands which, in the exceptionally dry conditions, have accumulated water soluble minerals that most places quickly wash into the sea or been incorporated in plants.

Including Lithium.

The NASA Earth Observatory presented satellite imagery of industrial harvesting of Lithium in large evaporation ponds in Chile.[1] .  The article reports that underground brine is pumped to the surface, where evaporation concentrates it.  The concentrated mineral brine is trucked to plants to be purified into Lithium and other products, shipped to China and the rest of the world.

From [1]
Of course, there is concern that these sources may be exhausted as the demand for batteries for electronics and electric vehicles grows.  In particular, it is very probable that  these industrial processes will deplete the underground brine faster than the limited inflow of snow melt can replenish it.

As in so many cases, we are indirectly burning water for fuel, which does not seem sustainable for too long.


  1. Adam Voiland, Where Batteries Begin, in The Earth Observatory. 2019. https://earthobservatory.nasa.gov/images/144393/where-batteries-begin

 

Sonic Flower for Bat Pollinated Plants

We are all worried about our pollinators.  Bees and other insect pollinators are dying off, probably at least partly due to human introduced chemicals.  But other species pollinate plants, including bats.

As we all know, flowers have coevolved with pollinators, advertising the joys to be found, luring visitors who pickup and drop off pollen to fertilize the plants.  Food in exchange for transport—everybody wins.

For us and many animals flowers are beautiful; colorful and scented. Possibly the most beautiful thing on our planet (which really should be called “Flora” rather than “Earth”).

But what about bats?  Our flapping night flying friends live in the dark, and generally can’t see very well.  Instead, they navigate and communicate sonically.  The point is, all those pretty flowers are mostly lost on our bat-friends.

This winter I read about a cool plant that lives in Cuba, Marcgravia evenia [2]. This plant has leaves with a concave, dish shape that resembles artificial antenna dishes. The study showed that this leaf shape indeed acts as a sonar beacon, strongly reflecting sounds akin to bat sonar in one direction.

The leaves grow near the flowers being advertised to the bats.  The study demonstrated that these reflectors are indeed a guide to bats, attracting them via sonar to the location of the flowers.

Flowering inflorescence of Marcgravia evenia. (A) dish-shaped leaf, (B) ring of flowers most of them in the male phase with anthers shedding pollen, (C) cup-like nectaries . Credit: Image © Ralph Mangelsdorff

The researchers note that the unusual shape and position of these leaves is disadvantageous for photosynthesis, suggesting that the promotion of pollination outweighs the lost productivity.  They also comment that there does not seem to be any other plausible function for these leaves.

They suggest that, like flowers, this mechanism benefits both species. The plants are relatively rare, and gain a very efficient pollination vector from the bats. The bats gain a guide to a food source, and one that is not as “visible” to other species.  In all this seems like a mechanism coevolved with bat sonar.

Cool.

“we expect to find other plant species that use equivalent or perhaps even fundamentally different acoustic signaling to attract their bat pollinators. “( [2], p. 633_

I’ll note that the flowers themselves are bright red and shaped to attract hummingbirds.  This plant is a belt-and-suspenders guy—more than one advertisement, more than one pollinator species.


  1. Susan McGrath, Call of the Bloom. National Geographic, 225 (3):127-139, 2014. https://www.nationalgeographic.com/magazine/2014/03/bat-echo/
  2. Ralph Simon, Marc W. Holderied, Corinna U. Koch, and Otto von Helversen, Floral Acoustics: Conspicuous Echoes of a Dish-Shaped Leaf Attract Bat Pollinators. Science, 333 (6042):631, 2011. http://science.sciencemag.org/content/333/6042/631.abstract

A Rainy Day on Titan!

File under:  We Must Go To Titan!

While the Cassini Mission was the usual NASA Big Science circus [2], Titan seems to be a pooch that can’t be screwed.  Lakes!  Clouds! Rain and Snow storms!

The Cassini mission finished with its final spiral and death swoop in 2017 and the fruit of those last close up observations is coming out now. The fall AGU featured a bunch of reports from the final orbits .

The last orbits included a sequence of passes near Titan  which recorded images and data from the North pole [1].  In Orbit T119 the North pole was obscured by clouds (which were not seen in earlier observations).  Two Titan days later, on T120 the clouds were gone and there were abnormally bright areas on the surface (again, not seen in earlier observations).  And by the next pass on T121 the bright areas were gone.

The researchers interpret these observations as evidence of rain storms, which left the ground wet and shiny for a while until the liquid soaked in and evaporated. [1]

Naturally, this is not water rain as on Earth, but rather Methane and other Nitrogen compounds rain.  But it does seem to confirm that Titan has weather, and that it is recognizably similar to our own weather.

We were pretty sure there was weather on Titan, but this is the first direct observation of a storm.  There is obviously a lot more to learn about Titan’s weather.

Of course, this findng suggests that, when we do send robots to Titan, they will need to (autonomously) keep and eye on the weather!  OK, the weather is mostly slow moving, but then our autonomous explorers are usual slugs, too.

in particular, proposed autonomous helicopter explorers  may have to contend with some serious bad weather, at least at the poles.  The notion that the low gravity and dense atmosphere make Titan ideal for helicoptering may prove a bit premature  [3].

Cool!  (Technically, very, very cool – -179 degrees C!)


  1. Rajani D. Dhingra, Jason W. Barnes, Robert H. Brown, Bonnie J. Burrati, Christophe Sotin, Phillip D. Nicholson, Kevin H. Baines, Roger N. Clark, Jason M. Soderblom, Ralf Jauman, Sebastien Rodriguez, Stéphane Le Mouélic, Elizabeth P. Turtle, Jason E. Perry, Valeria Cottini, and Don E. Jennings, Observational Evidence for Summer Rainfall at Titan’s North Pole. Geophysical Research Letters, 0 (0) 2019/01/16 2019. https://doi.org/10.1029/2018GL080943
  2. Ralph Lorenz and Jacqueline Mitton, Titan unveiled Saturn’s mysterious moon explored, Princeton, N.J., Princeton University Press, 2008.
  3.  Evan Ackerman, How to Conquer Titan With a Nuclear Quad Octocopter, in IEEE Spectrum – Automation. 2017. https://spectrum.ieee.org/automaton/robotics/space-robots/how-to-conquer-titan-with-a-quad-octocopter

 

Ice Worlds, Ho!

Ancestors of Kangaroos Could Hop

Kangaroos are wonderfully weird animals, hopping swiftly across flat country with an unmistakable gait (not to mention counterbalancing tail).

So how did this locomotion evolve?

This winner researchers from Sweden (!) report on fossils from 20 million years ago that they identify as ancestors of contemporary kangaroos [2].  These animals are similar to ancient “giant tree rats”, which is a great name for a band, but also seems to be the ancestry of kangaroos.

The new study examined the skeletons indicate that these animals were arborial, climbing and living in trees.  However, modelling the skeletons suggests that they were capable of hopping and other familiar kangaroo locomotion (including “pentapedal”, i.e., tail-ful walking(.

“We, therefore, prefer to interpret our results as indicative of comparable gait versatility in ancient fossil macropodoids, which potentially employed higher-speed bipedal hopping and/or quadrupedal bounding, in conjunction with pentapedal progression or asynchronous walking at slower speeds.” ([2], pp. 8-9)

From the limited fossil record, it isn’t clear how these animals lived and moved, or what evolutionary pressures may have influenced their anatomy and behavior.  The current study is based on statistics, but the samples are small and pretty iffy, so the results must be taken with a bit of care.

However, if these findings hold up, it seems that the basic ability to hop was present a very long time ago.  And if so, then contemporary kangaroos would have evolved to be extreme exemplars of these traits, adapting to the progressively drier climate of the last few million years.

This hypothesis reduces the mystery of how such an amazing adaptation could develop so rapidly.  Of course, it makes the earlier history more complicated.  However long legged hopping might have first appeared, it seems that some to these “giant tree rats” adapted to living in trees for a long time, yet retained the ability to hop on the ground.  How did these animals really live?


One notable point about this research is that the team refrained from assigning the specimens to a specific taxon.  As in most paleontology, the evidence is sparse—very sparse—so taxonomic assignments are quite iffy. But people seem prone to rush to give things a name, often coining new taxonomic labels, which are then overthrown by later research.

The Swedish researchers recognize that the fossils they studied are similar to some poorly described species, but there simply isn’t enough data to say how the sparse finds might be related to each other.  So they “deferred a formal classification”, referring to the specimens by their catalog numbers.  Good for them!

“we have deferred a formal classification herein because these remains cannot yet be distinguished from those of the closely related Propleopinae (extinct ‘giant rat-kangaroos’) […], whose postcranial osteology is virtually unknown” ([2], p. 10)


  1. Helen Briggs, When did the kangaroo hop? Scientists have the answer, in BBC News – Science & Environment. 2019. https://www.bbc.com/news/science-environment-47130734
  2. Wendy Den Boer, E. Campione Nicolás, and P. Kear Benjamin, Climbing adaptations, locomotory disparity and ecological convergence in ancient stem ‘kangaroos’. Royal Society Open Science, 6 (2):181617, https://doi.org/10.1098/rsos.181617

PS.  More great ideas for band names:

Giant Hopping Tree Rats
Kangaroo Ancestors
Prehistoric kangaroos
(Pretty much anything with “kangaroo” in it!)

 

 

Starfish die off on Pacific Coast

The oceans are warming.  This is not good for most lifeforms on Earth, and certainly problematic for everything that lives in the ocean.

This winter a team of researchers report on the recent decline in sea stars [1].  Since 2013, there has been a large decline in the numbers of these predators along the Pacific coast of North America.  This is attributed to “sea star wasting disease” (SSWD)  More than twenty species were affected, and evidence suggests a virus.

In addition to the alarming effects, these animals are important predators on sea urchins, so losses may be expected to lead increased numbers of sea urchins, which damage the ecosystem.

What triggered this large, sudden, widespread multispecies epidemic?

The new research shows that the catastrophic dying followed the onset of an episode of extremely warm sea surface temperature.  In fact, looking in detail at the whole area over several years they found a very clear tie to warming in a location, which was followed by massive dying about 60 days later.

“Our statistical analysis provides evidence for anomalous temperature as a key facilitator of the disease-related declines in the shallow nearshore waters, explaining more than a third of the variance by itself.” ([1], p. 2)

It appears that the dramatic warming is very stressful, and increased vulnerability to the viral infection.

The worst news is that the populations have not bounced back even after the temporary extreme temperatures.  Also, there are already signs of reduced amounts of kelp, likely due to increased predation by urchins.  As the researchers say, the loss of these species will have a cascading effect on the whole ecosystem.

“Cascading effects of the P. helianthoides loss are expected across its range and will likely change the shallow water seascape in some locations and threaten biodiversity through the indirect loss of kelp” ([1], p. 5)

This event is yet more evidence that steady warming average temperatures of the Earth’s surface and atmosphere will result in more extreme short term events. Even a relatively brief hot spell can tip a species or ecosystem into a catastrophe which is permanent, and far reaching.

The only good thing about this story is that the reported research was triggered by a spontaneous gift from high school kids (in Arkansas—thousands of KM from any sea start).  This funding led to matching, and spurred the research effort.  As a lead investigator put is, these kids “just needed to know those stars were there.” [2]

Sigh.  Now I have to recall that the last time I was in California, I really didn’t see any sea stars on the rocks.  I hadn’t realized how widespread this is, nor that I may never see sea stars again.

I am not amused.


  1. C. D. Harvell, D. Montecino-Latorre, J. M. Caldwell, J. M. Burt, K. Bosley, A. Keller, S. F. Heron, A. K. Salomon, L. Lee, O. Pontier, C. Pattengill-Semmens, and J. K. Gaydos, Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides). Science Advances, 5 (1):eaau7042, 2019. http://advances.sciencemag.org/content/5/1/eaau7042.abstract
  2. Kendra Pierre-Louis, Scientists Single Out a Suspect in Starfish Carnage: Warming Oceans, in The New York Times. 2019: New York. p. D3. https://nyti.ms/2Sehn3n

 

Climate Effects Of The Depopulation of Americas

I tend to be rather cautious about grand theories connecting everything to everything.  So I wanted to look very closely at a new study arguing that “America colonisation ‘cooled Earth’s climate’” [1].

This winter researchers from the UK report evidence that the “Great Dying” in the Americas following European contact caused a period of global cooling [2].

“The Great Dying of the Indigenous Peoples of the Americas resulted in a human-driven global impact on the Earth System in the two centuries prior to the Industrial Revolution. “ ([2], p. 13)

Following the contact and invasions of the early 1500’s, vast numbers of Americans died from European diseases, particularly in the Caribbean, Southeast US, Central America and Northern South America.. This depopulation had crippling effects on the social, political, and economic lives, and left the people open to relatively easy conquest.

The new paper seeks to estimate the ecological effects of this massive tragedy.  Specifically, the sudden disappearance of the human inhabitants led to large areas of land reverting from agriculture and other human uses to regrown forests.  In short, the paper interprets this as an accidental episode of mass reforestation.

Coinciding with this era, analysis of ice cores indicates a drop in atmospheric CO2, and historical records document a cool period, the Little Ice Age. Are these events connected?

This hypothesized connect involves a chain of connections. First, the pre-Colombian population would have to be large enough, and use enough land for the dieback to have an impact.  Second, the dieback and putative reforestation would have to be large enough to account for the uptake of that much CO2.  The study musters evidence for these factors, and models the probably effects on climate.

There are limited historical records from the pre-Colombian period, and no population censuses.  However, many methods have been used to estimate the populations of the Americas from archeological remains.  Combining these estimates, this study finds the population to be something like 60 million people (which might have been about 10% of the world’s human population).

“all 1492 CE population estimates require data to be combined with assumptions to arrive at estimates. “ ([2], p. 15)

Other studies have estimated the amount of land used to support these populations. These estimates are difficult to make precisely, because they rely on assumptions about not only populations, but also agricultural and cultural practices.  This study proposes that the total land under human use was about 50 million hectares (about the extent of France or Texas).

The Great Dying was a massive disaster for the American peoples, but estimates of the magnitude of the disaster vary. This study considers a number of studies and takes the median of the estimates:  which is 90% death rate!  This would make the post contact (circa 1600) population about 6 million people, which is at the low end of previous estimates.

Finally, when there was a depopulation, the land use reverted to forest.  Obviously, this process is specific to different locations. In some locations, there is evidence of the reduction of fires, which may be due to the end of intentional burning. Archaeological pollen indicates that some areas had significant reductions in cultivated plants at the time of the die off.  There is also archaeological evidence of abandoned settlements and apparent agricultural and other infrastructure.

Taking the estimated population decline and the estimated cultivation per capita, this study suggests that over 50 million hectares of agricultural land was abandoned due to depopulation.  (This is about 1% of the total land of the Americas.)

These estimates rely on a variety of assumptions and imperfect data.  The total abandoned land is higher than some estimates, but roughly in the midst of other estimates.

So, if 50 million hectares reverted to forest in a relatively short period, what might the effect have been?  The researchers indicate that carbon uptake increases rapidly in the first 20 years of such a transition, and slower after that.  With plausible estimates for different areas, this study yields an estimate of about 7.4 petagrams of Carbon sequestered in the abandoned lands.  This is higher than some estimates, partly because it depends heavily on estimates of the population loss and corresponding area of abandoned land.

At the end of this long chain of inference, the estimated Carbon uptake corresponds to a decrease in atmospheric CO2 of 3 ppm or more.

In fact, ice core data shows a sudden decrease of atmospheric C02 during that period. How much of this can be attributed to the effects of abandoned land, rather than other sources? The researchers argue that the isotope data from ice cores indicates that the decrease in atmospheric CO2 during the was due to uptake in soil and vegetation

“This unusual event of a rapid and large increase in terrestrial carbon stocks is consistent with a role for secondary succession following epidemics in the Americas after the arrival of Europeans, although there are other potential interpretations in the literature which we discuss in the next section. “([2],  p. 27)

Data from many studies shows that there was atmospheric cooling coinciding with the decreased atmospheric CO2, indeed “1577-1694 CE is the only period of significant global cooling within the past two millennia”, and is recognized as “the Little Ice Age”. This cooling is in alignment with theoretical models of the effects of decreased CO2. The researchers find that is no evidence for similar changes in total solar irradiation or volcanic aerosols during this period.

“Through multiple routes we arrive at the conclusion that LUC [land use change[ in the Americas played an important role in driving lower atmospheric CO2 in the late 1500s and early 1600s.” ([2], p. 29)

Altogether, the study concludes that the Little Ice Age was probably caused by the depopulation of the Americas and corresponding changes in land use.

This result, if sustained, is an interesting perspective on the complex world-wide effects history of the European invasion of the Americas.  It is already known that the transfer of species (e.g., food plants) changed diets and health.  It is also known that the massive transfer of precious metals, particularly silver, generated substantial inflation throughout Europe, and increased trade between China and the world.

If the American genocide triggered or exacerbated the Little Ice Age, then its indirect effects included bad weather and famine in Europe and elsewhere, with concomitant social stress and unrest. Karma, anyone?


This is a fascinating study, connecting two obvious dots with a line through a variety of evidence.  (I’m a big fan of using multiple lines of evidence.)  They make a plausible case.

We’ll have to see how well this holds up.

There are competing hypotheses, starting with disagreements about the supposed dating of the “Little Ice Age”.  And while 1492 is pretty firmly dated, the course of contact and depopulation (and subsequent population increase from European immigration) are far harder to date because they occurred over the whole western hemisphere for several centuries.

In addition, estimates for the pre-contact populations and land us are uncertain, as are the estimates for the magnitude and pace of the die off.  In short, refined estimates for these factors could change the conclusions.

And, of course, the climate models used to connect the dots from depopulation to cooling are uncertain. However plausible the hypothesis, there is a huge amount of uncertainty in the argument.

Nevertheless, this study certainly lays out an interesting case. The Little Ice Age does not seem to have a clear cause.  And the Great Dying was a once-in-history “cause”, potentially of just the right magnitude.  If there isn’t a connection, it’s a hell of a coincidence.

The authors also point out that the scenario in this study gives perspective on current preoccupation with reducing atmospheric CO2 [1].  This was a massive unplanned reforestation (of an area equivalent to all of France) which had a strong, almost immediate effect on the atmosphere and climate.  That’s good, but only a drop in the bucket compared to current emissions of Carbon.  It’s going to take a heck of a lot of reforestation to put a dent in our current situation.


  1. Jonathan Amos, America colonisation ‘cooled Earth’s climate’, in BBC News – Science & Environment. 2019. https://www.bbc.com/news/science-environment-47063973
  2. Alexander Koch, Chris Brierley, Mark M. Maslin, and Simon L. Lewis, Earth system impacts of the European arrival and Great Dying in the Americas after 1492. Quaternary Science Reviews, 207:13-36, 2019/03/01/ 2019. http://www.sciencedirect.com/science/article/pii/S0277379118307261