A Tragic Loss: E. O. Wilson has Died

E. O. Wilson examining a leaf. He advocated for a world where all species have the space and resources to survive. Photo courtesy of National Geographic.

E. O. Wilson died yesterday at the age of 92. The sciences of entomology, biodiversity, biology, ecology, and evolutionary biology have suffered a huge loss. Beyond those specific scientific disciplines, the world has lost an amazing science communicator and advocate of nature.

Edward Osborne Wilson was born in Birmingham Alabama, USA on June 10th, 1929. He grew up chasing snakes and birds and insects around Birmingham, Washington D.C., the various other towns he grew up in (his parents were divorced and each moved several times during his childhood) and also on the many hiking and camping trips he took into the surrounding areas. This early interest in the natural world solidified into an obsession with ants which he studied throughout his undergraduate and graduate work.

In his early career, E. O. Wilson worked with another scientist named Robert MacArthur to develop a way of explaining why species tend to be scattered across the planet in the patterns that we see. Originally, these two focused on explaining, with mathematical equations, why and to what extent big islands have more species than small islands, and islands close to continents have more species than remote islands. This set of concepts became known as Island Biogeography. It was quickly recognized as having much wider applications. Not only did it work for islands, but for other features as well. Lakes could be seen as ‘islands’ set in land masses. And even further, nature preserves could be seen as ‘islands’ set in inhospitable and highly modified landscapes. Island biography can be used to predict how large a nature preserve is needed to save a certain number of species. It can be used to determine how far apart nature preserve ‘islands’ can be and still maintain viable populations of animals, plants, and fungi.

On top of island biogeography, E. O. Wilson pioneered work in sociobiology by exploring how behaviors of insects and behaviors of humans and other vertebrates are similar in many ways. He popularized the term biodiversity and spent considerable effort in working toward the preservation and documentation of life on this planet.

E. O. Wilson was also a tremendous writer. His list of written works includes over 30 books and 430 scientific articles, and these span a range of scientific and popular science material. He made scientific topics accessible to a wide range of public readers and inspired countless people (including myself) to pursue these topics further. His book “Letters to a Young Scientist” is one of the best and most inspiring books I have ever read.

Without a doubt, Wilson was a giant in the field. He developed really impactful ideas. He mentored a huge number of other scientists. To popularized science to the wider world.

We have all lost a treasure.

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Wasp Mantidfly (yes you read that right)

Every now and again, I learn about a creature that I have never heard of before that so surprises me that I can’t stop thinking about it. The most recent occurrence of this was about a month ago when I stumbled upon a picture online of a species of insect that just does not seem possible. it is called a Wasp Mantidfly (Climaciella brunnea). Firstly, the name of this insect is one of those names that just gets better and better as you read through it. Secondly, the name of this insect fits its appearance perfectly. I mean look at this thing!

A Wasp Mantidfly (Photo Credit: University of Minnesota Extension).

Learning about this insect has just gotten better and better the deeper I have gone! And it starts with a bit of irony because while the name fits the appearance of this species to a T, with its very wasp-like black and yellow striping and narrow waisted body, its very mantis-like front legs, and its very fly-like wings, it is actually not related to wasps, mantids, or flies! Perfect, and I right!?!

The Wasp Mantidfly is one of about 400 species of Mantidfly (sometimes also called Mantisfly) found around the world with 13 occurring in the USA. They are actually in the family that includes lacewings and antlions. And these Mantidflies have evolved a ton of amazing adaptations!

The first set of amazing adaptations have to do with the larvae. The first is that most Mantidfly larvae are parasites that eat spider eggs. The larvae cannot get through the silk strands that a mother spider spins to wrap her eggs in. So, the larvae gets itself wrapped into the spider egg case as the eggs are being laid. How the larvae is able to do this brings us to the second amazing adaptation – hypermetamorphesis. Regular metamorphesis is when an organism goes through several distinctly different life stages in its lifecycle. A classic example is the butterfly that lays an egg that hatches into a caterpillar that forms a chrysalis that emerges as an adult butterfly. Hypermetamorphesis is when an organism goes through those same life stages and then some! In the Mantidflies, the larvae actually have a couple of forms with the first one being a long-legged and very mobile form, and then the second form being more grub-like. The first mobile stage allows the larvae to seek out a spider and grab on for a ride. The trait of riding around on another animal is a third amazing adaptation – phoresy. Phoresy is when one organism rides around on another organism. The Mantidfly larvae hangs around on the underside of leaves and other places that are likely to have a spider walk past, and when a spider does pass by they climb aboard. If the spider is a male, the larvae will ride around until the male spider mates at which point the larvae will leave the male behind and ride around on the female. Once the larvae is on a female spider, it gets carried around on the female spider until she lays eggs. At which point the larvae maneuvers itself so that it gets wrapped into the egg-case. Once securely inside, it changes in the more grub-like larvae form and then begins eating the spider eggs. The larvae remains inside the egg-case to pupate and then emerge as an adult Mantidfly that is able to chew its way out of the spider silk and go on with its life.

The adult Wasp Mantidfly, specifically, has a more amazing adaptations! One that it is a Batesian mimic. This means that its coloration has evolved to look like a dangerous wasp, but is in fact harmless itself. If you are curious about Batesian mimicry, I posted a video on my YouTube channel on mimicry. A second amazing adaptation comes into play when the adults are looking for mates which occurs in the spring. The males release an aggregation pheromone. This is a chemical that female Wasp Mantidflies can detect and that attracts them to the male. One advantage of these aggregation chemicals is that it may help the Wasp Mantidflies to determine if an insect is a potential mate or a wasp that they look so much like! Yes, Batesian mimics have to worry about mimicry too. And lets not forget about those incredible front legs! In an impressive example of convergent evolution, the Wasp Mantidfly uses its front legs in the same way that a Preying Mantis does which is to grab other insects to eat.

All in all, these creatures look like they might have been produced in Dr. Frankenstein’s laboratory, but are actually an amazing product of evolution, and I really want to see one!!!

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Are Humans Evolving?

Are humans still evolving? Have medical advances and the luxuries of modern life removed the pressures that natural selection might exert and so remove the driver for humans to change from generation to generation?

Sketch of the human forearm indicating the median artery (Image Credit: Professor Maciej Henneberg

Several examples can be pointed to which indicate that we humans are still evolving from increasing head size to the reduction in frequency of wisdom teeth. And a new example has just been discovered!

Researchers at Flinders University and the University of Adelaide (both in Adelaide, Australia) have discovered that some adult humans today have three arteries that bring blood to their forearm and hand, while the rest have only two. And the percentage of the population that has three is increasing. These results were published in the Journal of Anatomy in September 2020.

We all had three arteries in our forearms when in utero which are called the ulnar artery, the radial artery, and the median artery. But most adults only have two because the median artery (the one in the middle) generally disappears as a fetus develops. However, sometimes it never disappears, and adults will have a functioning median artery. This variation in development is where the researchers focused their attention.

Anatomists (people who study anatomy) have noted that the median artery disappears sometimes, but not always, for well over a hundred years. Some of these anatomists examined adults born in the 1880s and noted that about 10 percent of them still had their median artery and 90 percent has lost theirs. Researchers from those two universities in Australia mentioned above read these reports and wondered if those numbers had changed. They examined the forearms of adults born in the late 1900s and found that about 30 percent retained their median artery while the percent that lost their median artery was down to 70 percent.

Looking at those numbers, it might not seem very dramatic, but a 20 percent difference over just a few generations is pretty significant in evolutionary terms. If this rate of change continues, everyone born 80 years or more from now will have a median artery as adults. When most people have a median artery as adults, medical standards will need to change. At that point, having a median artery will be the normal condition, and no longer be considered a variant as it is today.

No one is sure why this trait is being favored. Having three arteries that feed the hand does allow for increased blood supply. While it might be tempting to try and explain this change as a reflection of how important hands are to our survival, that idea is not supported by any data. In fact, hands have been important for human survival since before we evolved into humans, so even the idea is a bit weak. Whatever pressures are causing natural selection to favor the retention of a median artery into adulthood is an interesting question that stands open.

This example of the median artery shows that humans are still evolving and that natural selection continues to influence our species even if we don’t understand why it may be occurring.

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Invasive Mute Swans

Mute Swans (Cygnus olor) are a species that is growing more and more numerous, and this is a problem.

Mute Swans are the “classic” swan from stories and art. They are large and showy and beautiful and these traits are exactly why they have been introduced to North America. Birds were brought from Europe in the 1800s and released in parks, gardens, etc. as ornamental additions (New York was the original release area). These birds have since reproduced and spread across the continent as far north as New Hampshire, as far south as Florida, and as far as west as California.

Adult male Mute Swan (Cygnus olor). Source: USFWS digital library.

They are becoming problematic for several reasons. One is that they are quite aggressive, and will chase and bite humans if that human trespasses on the swan’s territory. Another is that they consume quite a bit of food. They are big birds reaching up to 25 to 30 pounds, and that means they eat about eight pounds of aquatic vegetation every day. That is food which is then not available to native birds, and it disrupts habitat for native birds, mammals, fish, and other species. And a third reason is that the swans are directly aggressive to other species of bird driving them off nests, breaking eggs, and killing the chicks of other species, and so displacing those other species from areas where they would otherwise live. With habitats becoming ever smaller and more fragmented, this can mean the native species can be left with no where to go.

These problems have all contributed to Mute Swans being added to California’s restricted species list in 2008. This listing means the birds cannot be imported, transported, or possessed in the state without a permit. This has not completely prevented the swans from beginning to become established in California. Small populations can be found in Petaluma and the Suisun Marsh. I suggest that removing this species while the population is still small is the best course of action. There is every reason to suspect that the population will grow, and as it does so, the problems listed above will become more and more apparent. However, control will become more and more difficult.

One interesting thing about Mute Swans in North America is that they do not migrate very much. There are certainly some, relatively short, seasonal movements that occur in some parts of the continent, but not much. Certainly nothing compared to the long migrations that Mute Swans in Europe engage in. The evolution of this behavior in a novel environment illustrates how different geographic regions can cause a species to adapt and change. This behavioral evolution could then lead to the evolution of a new species, if it persists and becomes dramatic enough.

So, what can you do to help native birds and habitats, and prevent Mute Swans from taking over? If you spot a Mute Swan in California, contact the California Department of Fish and Wildlife – Invasive Species Program by sending an email to: invasives@wildlife.ca.gov or calling 886-440-9530. Together, we can act as citizen scientists to gather data that tracks where these birds are and how they move around. This data will help us all make the best and most informed decisions we can about this species.

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Partitioning the Trees

A few years ago I wrote a post on niche partitioning among herons and egrets. That post was inspired by watching several species of herons and egrets foraging for food along Putah Creek near Davis, CA, and the resource they were partitioning into niches was food.

Recently, as part of my work at the Sacramento-San Joaquin Delta Conservancy, I encountered another example of niche partitioning by herons and egrets. This time, the resource these birds are partitioning into niches is nesting trees.

One of the grants that I manage at the Delta Conservancy is at the Cosumnes River Preserve and it includes and grove of large Valley Oak trees that many herons, egrets, and cormorants use as a rookery (a rookery is a colony of breeding animals, generally birds). One way that the various species have evolved to utilize the same trees, and yet avoid directly competing with each other, is for each species to utilize a different part of each tree to nest in.

Great Blue Herons typically nest on the very tops of the crowns of trees, Great Egrets typically nest only in the upper one-third of the canopy, Snowy Egrets typically nest in the middle one-third of the canopy, and Black-crowned Night-Herons prefer to nest in the lower one-third of the canopy (see the image below).

Niche partitioning of nesting locations within a tree by heron and egret species

I think this stratifying of nesting locations is amazing! Species have evolved to fill so many different niches, and so many niches can be divided into finer and finer gradations. I wonder if there is really any limit to how many species can evolve, and how complex an ecosystem can develop, in a give location.

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Evolution Brings Extinct Bird Back to Life! Except it Didn’t

A news story has been circulating a fair bit in the past couple of weeks. This story has been picked up by numerous news and science outlets. How it is being reported and explained is just plain misleading and inaccurate.

The Aldabra Rail is a subspecies of the White-throated Rail.

Here are a few titles that show how the subject is being covered.

Science Magazine – Evolution Brings Extinct Island Bird Back into Existence

Smithsonian Magazine – How Evolution Brought a Flightless Bird Back from Extinction

CBS News – An Extinct Bird Species Has Evolved Back into Existence, Study Says

From these titles, and from the bodies of the articles themselves, readers would think that the same species of bird existed at some point in the past, went extinct (as in died out completely), and then re-evolved!

That does not happen.

Here is what actually did occur.

The small atoll of Aldabra is a pretty spectacular spot. It is very remote. It is quite beautiful. It is home to a bunch of unique animals found no where else on earth. It has one of the longest fossil records on any island in the Indian Ocean.

That fossil record includes a lot of the animals that have called the atoll home over the past few million years. One of those animals was the Aldabra Rail. This rail was a small flightless bird that was probably found hunting through reed beds along the edges of water. The Aldabra Rail went extinct about 136,000 years ago at about the same time that global sea level was rising and submerging oceanic islands like Aldabra. After a few thousand years, sea level dropped and Aldabra became an exposed island once more. Not long after that fossils of a rail on Aldabra start showing up again.

There are a couple of possible explanations. One is that some remnant population of the Aldabra Rail hung on, some how, and did not die. These were flightless birds, so it is not clear how this might have happened, but perhaps a small population managed to survive on a floating raft of vegetation long enough to reach an exposed bit of land. This seems like a very long shot. It is much more likely that the Aldabra Rail simply died out completely. It went extinct.

The other possible explanation is much more likely and widely understood and accepted, and it is this: the Aldabra Rail went extinct when the atoll went under water. Then after it re-emerged, a group of birds likely from the same parent stock of the original Aldabra Rail re-colonized the atoll (quite probably from Madagascar). This new group of colonizers eventually became flightless and filled the same, or very similar, ecological niche as the original Aldabra Rail.

This is a process called iterative evolution and it is pretty rare. The definition of iterative evolution is: the evolution of similar or parallel structures in the development of the same main line.

But iterative evolution does not produce the same species twice. It may produce similar species, but to produce the same species twice would require starting with the same gene pool twice. The group of birds that first colonized Aldabra, and became the Aldabra Rail 1.0, had a unique combination of genes to work with. The group of birds that later colonized Aldabra, and became the Aldabra Rail 2.0, had a unique combination of genes to work with. Those two combinations of genes may have been similar, but they were not the same. Therefore the decedents of those two groups would not be the same.

I really think that the implications of how this story is being reported is really misleading and possible even damaging.

Misleading because they imply that a species can evolve twice. To go back to the definition of  iterative evolution, it the evolution of “similar or parallel structures…” Similar or parallel structures are not the same as identical species. Two rails that evolved at different times in the same place and that are both flightless, are not the same species.

Damaging because there is weight to the idea of extinction. Extinction is forever. It means that an entire evolutionary lineage has ended, and any potential future that that lineage may have had is gone. If the idea of extinction becomes an impermanent one, it looses its urgency and tragedy. People may well not worry about extinction as that species can just re-evolve. No harm, no foul.

Again, no species can ever occur twice. Once a species goes extinct, that is it for that evolutionary lineage. Even if some other lineage emerges that is close, it will not be the same and will not have the same evolutionary trajectory or potential.

When reporting on science, I feel strongly that the ideas behind the science should be accurately represented. I think it is especially distressing when the sources of the misrepresentations are otherwise reputable sources for science.

I hope the current Aldabra Rail has a long future filled with descendants, and I mourn the loss of the previous rail of Aldabra and the lineage it might have left behind, but never will.

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Information is Important

Information is important. With information each of us as individuals, and our society as a whole, can learn about the world. With information, we can all make decisions that make sense. With information, we can all discuss ideas.

Without information none of that is possible. Without information, we are, at best, at the mercy of our current, limited knowledge, and our base instincts. Without information we are, at worst, at the mercy of the limited knowledge and instincts of someone else.

This is why the gag order, and insistence that all reports and data be pre-screened before release to the public, issued by the President to the EPA are so concerning to me, and I think should be so concerning everyone else. This is exactly the kind of action that limits access to, and spread of, information. It will only hamper all of our abilities to operate as rational, critically thinking individuals. It is the kind of action that is put in place to control what we, as citizens, know and when we know it. This is censorship and it has no place in science or a free society.

#thisisnotnormal

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A New Jay in Town

The American Ornithologists Union (AOU) is, among other things, the arbiter of avian taxonomy in Middle and North America. They are the organization that rules on whether a species should be split in two, or if two species should be lumped together. They are the organization that rules that Loons are no longer the most basal group of North American birds, but that they group that contains ducks, geese and swans holds that honor. The AOU releases all these decisions in the form of annual Supplements to the official AOU Checklist (which is a complete list of all bird species and subspecies listed in taxonomic order).

A lot of science has to be done before the AOU makes any of these ruling, and these ruling are subject to change as more science is done, but at any given time, the current AOU Checklist represents the best available knowledge on how many species of birds there are and on how they are  all related to one another.

Well, the AOU just released their most recent Checklist Supplement and it has, among the many updates and changes, an interesting change for California. Since that is where I live, I am particularly interested in this one. It concerns a common member of the corvid family that anyone who has spent any time outside has seen. The Western Scrub-Jay (Aphelocoma californica).

This species has actually already had an interesting history in the taxonomy world. Before 1995, there was one species recognized as a Scrub Jay (Aphelocoma coerulescen). This species was found across the western USA and also in Florida. In 1995, the AOU split the Scrub Jay into three distinct species. They were the Florida Scrub-Jay, which retained the original scientific name (Aphelocoma coerulescens), recognizing the Florida population as genetically distinct; the Island Scrub-Jay (Aphelocoma insularis) recognizing the population found on the Channel Islands off the coast of southern California as genetically distinct; and the Western Scrub-Jay (Aphelocoma californica) which included all the remaining populations in the western continental USA.

California Scrub-Jay (Photo credit: Frank Lang)

Now, in the most recent AOU Checklist Supplement, the Western Scrub-Jay has been split again. We now have the California Scrub-Jay (Aphelocoma californica) recognizing that the population along the Pacific Coast is actually genetically distinct from the Woodhouse’s Scrub-Jay (Aphelocoma woodhouseii) found in the inter-mountain west.

Woodhouse’s Srcub-Jay (Photo credit: Robert Mortensen)

In addition to the genetic distinctions, these two new Jay species also have behavioral and morphological differences. The California Scrub-Jay is darker in color, generally lives in Oak woodlands, and eats a range of seeds including a lot of acorns and so has a heavier bill. In contrast, Woodhouse’s Scrub-Jay is lighter in color, generally lives in the Great Basin pinon-juniper scrublands, and correspondingly eat a great deal of pinon pine nuts and juniper berries and so have a slimmer bill.

So, update your life lists, start getting used to using the new four-letter codes of CSJA (now standing for California Scrub-Jay) and WSJA (Now standing for Woodhouse’s Scub-Jay, and not Western Scrub-Jay that it used to identify), and enjoy picking apart the finer levels of identification between these two newly recognized species!

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Dinosaur Feathers

Single feather, and a mite, preserved in Late Cretaceous amber found in Canada.

In the movie, Jurassic Park, humans are able to get dinosaur DNA from insects that were preserved in fossilized amber millions of years ago. Well, it has been very convincingly shown that any DNA that might get trapped in amber during the age of dinosaurs would degrade too badly over time to still be viable today. However, this does not mean that amber is useless in preserving amazing structures that we can find and learn from and marvel at.

A recent report that appeared in the journal Science is an excellent example of what I mean. Researchers examined a number of fossilized feathers that were preserved in amber during the Late Cretaceous. These feathers likely came from dinosaurs! And they are beautiful, having been spectacularly preserved in the amber that surrounds them. At this point, no one is exactly sure if these some of these feathers came from early members of what would become the bird lineage, or if they came from non-avian dinosaurs, but either way, the feathers are stunning. In fact, the feathers are in such high quality condition that even tiny features can be observed. Impressively, many of these tiny features on the dinosaur feathers look exactly like the tiny features one would see on the feathers of a modern bird. One example of this is the way that the barbs of some of the feathers twist like a corkscrew. This is a feature also found in modern water birds and may suggest that the dinosaur that those feathers came from lived in close association with water as well. The researchers can even take a stab at figuring out what color some the feathers were; colors that range from white to brown to black. This backs up a lot of other research that has suggested that dinosaur feathers probably had a wide range of colors and patterns, some of them quite bright and dramatic!

A feather found in Late Cretaceous Canadian amber. The dark masses all along the filaments are regions of pigment concentration. This feather was probably medium to dark brown.

Another exciting outcome of all these fossils is that they represent a range of stages in feather evolution. Some of the fossils are little more than very thin filaments, sometimes referred to as protofeathers (or dino fuzz). These protofeathers are probably some of the earlier stages in the evolution of the structures that would eventually become the tail feather of a Peacock or the crest feather of a Royal Flycatcher. These filaments have been found preserved in the rock surrounding other non-avian dinosaur fossils, but they have never been seen in such detail as they can be in the amber. Others of these fossil feathers show much more elaborate feathers that have many of the same complex features of modern feathers.

Follow this link: http://io9.com/5840854/dinosaur-feathers-discovered-in-canadian-amber to see more photos of feathers fossilized in amber. And next time you see a member of the only living lineage of dinosaurs (a.k.a. a bird), take a moment to think about the feathers that cover its body and to realize that millions of years ago, there were animals sporting feathers that look just about the same. Pretty amazing!

A cluster of 16 feathers preserved in Canadian Late Cretaceous amber.

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Powered Flight in Vertebrates

Powered flight, the ability to propel oneself through the air against the force of gravity, requires a great deal. From specialized bones to specialized skin, and everything in between, the demands of flight penetrate all aspects of an animals’ life. And yet, despite how mechanically difficult powered flight is to achieve, it has evolved three different times in vertebrate evolution, once in birds, once in bats, and once in the now extinct pterosaurs. One of the things that make the three different evolutions of flight especially interesting is that the three different groups accomplished the feat is such different ways.

A pterosaur wing has a large upper arm bone, two smaller forearm bones, a few wrist bones, and then four fingers. The first three are small fingers that have small claws at their tips and are free to move and grasp objects. The fourth finger is extremely long, extending all the way to the tip of the wing. The bones of this fourth finger are longer and thicker than the bones of the other fingers, and this is because this fourth finger supports the entire wing membrane. The wing membrane attaches all along the rear surface of the fourth finger, the rear surface of the arm, and then to the side of the trunk of the animal and even to the leading edge of the hind legs. That means that, when a pterosaur is in flight, the whole weight of the animal is being supported on once finger of each hand! Some pterosaurs got to an estimated 550 lbs (although most were about 25 lbs) with a 10 or 11 meter wingspan, so those are some strong fourth fingers!

A bat wing is the same upper arm bones of the pterosaur, but the hand is very different. Instead of supporting al the body weight of the animal on just one finger, all five of the fingers of a bat are elongated (the thumb is the only finger that is small and clawed and free to grasp). In between each of these fingers, and extending from the pinky finger to the body are membranes that the bat can stretch or fold as needed by moving the bones in its fingers, hands, and arm. Since all the fingers are sharing the load, each one is proportionately much finer and thinner than the fourth finger of a pterosaur. Additionally, bats have thin muscles that cover the surfaces of the membranes just beneath the skin. By tensing or relaxing these muscles, the bat has very fine control over the sharp and tension of the wing membranes, and this turns out to be very important in bat flight. It is not known if pterosaurs had similar muscles on the membranes of their wings, but it seems likely that they did.

A bird wing also has the same basic upper arm bones seen in the other groups, but instead of elongating bones and making them delicate and distinct, birds go the opposite direction. Most of the bones in the hand and fingers of a bird are fused together. This makes a structure that is short, thick, and strong. Out of this support structure extends feathers. Not a membrane made of skin like a pterosaur or a bat, but a completely different evolutionary innovation. Feathers, and flight feathers in particular, are strong and thin and light. Flexible enough to bend a bit to change shape, but rigid enough to support the weight of the bird and the forces of air-speed, drag, lift and gravity that all flying organisms have to contend with. In modern birds, muscles in the skin at the base of the feathers allow for independent control of each feather. This allows birds to have amazing control over the shape of their wing.

Flight is a fascinating example of how a complex structure or function can arise by natural selection. In these three cases, natural selection favored three very different, and ultimately successful, experiments in how to get an animal airborne. All three were very different solutions, which is worth remembering. Most of the problems out there, even really hard ones, probably have many different solutions, you just have to tinker and figure them out.

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