Monthly Archives: July 2014

For All Mankind

Today we celebrate one of humanity’s greatest accomplishments. On July 20, 1969 — 45 years ago today — Neil Armstrong and Buzz Aldrin became the first humans to set foot on the moon. It was the height of the cold war, and the United States poured a huge amount of effort into space exploration as a way of competing with the Soviet Union. The Soviets beat us at many milestones, but the success of our human missions to the moon won the space race soundly for the United States.

Although Armstrong and Aldrin were sent to the moon to beat the Soviets, the plaque they left behind reads, “We came in peace for all mankind.”

The Apollo 11 lunar plaque. Image from

“We came in peace for all mankind.”

It could have read, “We claim this land for the United States of America.”

Given the times, it could have read, “Screw you, commies.”

But it said “we came in peace for all mankind.” This was an accomplishment for the men who personally walked on the moon, but it was not just for those men. It was an accomplishment for the United States, but it was not just for the United States. It was an accomplishment for the human race. Though these men and the country they represented were raised up by this accomplishment, they raised up every human being along side them.

Earlier that year, on April 17, 1969, Dr. Robert Wilson (1914-2000), a nuclear scientist, appeared in front of a congressional committee to ask for money to build the “linac” particle accelerator at the National Accelerator Laboratory (now known as Fermilab) in Batavia, Illinois. Senator John Pastore (D-RI) asked him, “Is there anything connected in the hopes of this accelerator that in any way involves the security of the country?” Dr. Wilson responded that,

“It only has to do with the respect with which we regard one another, the dignity of men, our love of culture. It has to do with these things… Are we good painters, good sculptors, great poets? I mean all the things that we really venerate and honor in our country and are patriotic about…It has nothing to do directly with defending our country except to help make it worth defending.” [emphasis added]

Scientific discovery is not just a tool we use to invent products that improve our lives. The knowledge and discovery and exploration themselves improve our lives. Most people think that science can make us great through the technology that it leads to. It isn’t that this is untrue, but this is only part of the picture. Science makes us great because it is a great achievement of humans. The accomplishments of science enrich our lives in the same way that we are enriched by the accomplishments of great poets, great composers and great artists. We share in the pride of the accomplishments of our scientists and we appreciate the beauty and wonder of their works. Science can indeed help us build planes and bombs and rockets that allow us to defend our country, but the fact that we carry out scientific research is a part of what makes us great and worth defending.

In 1972, during the Apollo 17 mission — the last time anyone sent live people to the moon — astronauts took a picture of the Earth from orbit. Known as “The Blue Marble,” this is one of the most famous photographs ever taken.

The Blue Marble. Photo taken by the Apollo 17 crew. Image from

In 1990, the Voyager 1 spacecraft  photographed the Earth from 3.7 billion miles away — 40 times the average distance between the Earth and our Sun. The Earth is visible only as a tiny dot. This photograph became known as “The Pale Blue Dot” and inspired a book by Carl Sagan of the same title.

Photograph of earth taken from the Voyager 1 spaceprobe. Image from

On July 19, 2013, the Cassini spacecraft took a picture of Earth through the rings of Saturn. At the time of the photo, the people of Earth were encouraged to contemplate their place in the universe and smile for the camera. People all over the world took part.


Photograph from the Casini spaceprobe. Earth can be seen as a blue speck in the center right of the photograph, in between the rings of saturn. Image from

These photographs and events represent to us the collective accomplishments of the human species. Why would people in all corners of the Earth look up and smile for a photograph being taken too far away for their faces to be seen? Because they felt connected. These photographs do not particularly serve any scientific purpose, and they were not the point of these missions, but the photographs allow people to feel connected to the accomplishments that the photographs represent.

Consider if we discover an intelligent alien civilization at some point in the future. We might exchange some technology with them, and that might improve our lives. But to think of it only in terms of technology is missing the point. The discovery that we as intelligent life are not alone in the universe would profoundly change us. It would be the greatest discovery in all of human history.

Neil Armstrong died two years ago, so he is not able to share in today’s celebration, but his surviving family recommends a way to celebrate him:

“For those who may ask what they can do to honor Neil, we have a simple request. Honor his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down at you, think of Neil Armstrong and give him a wink.”

I encourage you to go outside tonight and wink at the moon. Remember the accomplishments of Neil Armstrong and Buzz Aldrin 45 years ago, but also think of the collective scientific achievements of all humans throughout time.



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10% Of Our Brains?

There is a new movie coming out later this month called “Lucy.” (See the trailer here.) The premise of this movie is that humans only use 10% of our brains, and Scarlett Johansson  gets superpowers by using more than 10% of hers. This idea that we only use 10% of our brains, but would be better if we used more, is a very persistent myth in our society.

Disclaimer: My point here is not to rain on anyone’s parade. I love science fiction movies, and if Luc Besson’s record is any indication, this one will probably be good. (Personal note: Luc Besson wrote and directed my favorite movie.) Even though I am a scientist, I am usually willing to suspend my disbelief for whatever premise the movie asks me to accept. I am not trying to convince anyone that they shouldn’t watch this movie or that it will suck because it gets some facts wrong. The release of this movie is just a convenient opportunity to talk about an oddly persistent myth.

Now back to the show…

My first exposure to this myth was probably as a child when I read the book My Teacher Fried My Brain — the second book in the My Teacher Is An Alien series. In this book, the school bully has his brain zapped by an alien device which makes him much smarter and a much more pleasant person. I can remember speculating later that very smart people like Albert Einstein probably used more like 50% of their brains.

But none of this is true. There have been several takedowns of the 10-percent-of-our-brains myth from a neuroscience perspective by people who are more qualified than I to discuss neuroscience. I am much more qualified to discuss this from an evolutionary angle.

Evolution is incremental. Traits evolve slowly over time, with each successive version of the trait being slightly better than the last. The brains of modern humans have a volume somewhere in the area of 1200 cubic centimeters (cc). Chimpanzee brains have less than a third of this volume. We evolved from an ape that was not exactly a chimpanzee, but we can use the chimp brain size as a point of comparison. Since our evolutionary divergence from our chimpanzee-like ancestors, our brains have tripled in size. This means that, during our evolution, individuals with 450cc brains survived and reproduced better than individuals with 430cc brains, and individuals with 500cc brains survived and reproduced better than individuals with 450cc brains. Our brains eventually grew to what they are now because the modern brain allowed individuals to survive and reproduce better than individuals that had anything less than a modern brain.

Human brain (top) compared to chimpanzee brain (bottom). Image from

The modern human brain is astonishingly expensive to build and maintain from a caloric standpoint. A typical adult male at rest requires 1800 Calories per day to function. That is, a man lying motionless but awake for 24 hours will burn 1800 calories just to maintain his body. This 1800 Calories is his “metabolic budget.” The metabolic budget is just the cost of every process within the body added up. Keeping the heart beating and the lungs breathing requires some of these calories. Replacing old, worn-out cells requires some more of these calories. The average adult male brain requires 414 of those Calories, which accounts for 23% of the total resting budget. Typical adult females require fewer Calories to function (1480) than adult males. The female brain requires about the same number of Calories as the male brain (400), but accounts for a slightly larger percent of the resting metabolic budget (27%).

Malcom Holliday (1986) studied the energetic cost of the brain at different stages of life. (The data above is his.) The brain is relatively more expensive at younger ages because the brain is growing very fast and because the brain accounts for a larger portion of the body’s overall mass.

Malcom Holliday (1986) studied the energetic cost of the brain at different stages of life. (The data above is his.) The brain is relatively more expensive at younger ages because the brain is growing very fast and because the brain accounts for a larger portion of the body’s overall mass.

Evolution is not wasteful. Acquiring enough energetic resources to survive was a big problem for our ancestors. Building a smaller brain would be less expensive. If the expense of building a bigger brain was not offset by the advantage it gives, it would never have evolved in the future. If humans suddenly found ourselves in an environment where our big brains were no longer an advantage for us, our brains would subsequently evolve to be smaller. (Remember that evolution does not always make things bigger, better and more complex.)

If the brain was larger (and therefore more energetically expensive) than it needed to be, individuals with a smaller brain would be able to spend that additional energy on other important things. They could spend it acquiring resources to support more offspring. They could spend it on growing bigger muscles and repairing more damage. Or they just wouldn’t require as much energy to survive and it would be harder to starve to death. This is to say that a brain that wastes 90% of its potential could not possibly evolve. Compare this to a centipede that only used 10 of its 100 legs or a cheetah that had the anatomy and physiology to run 70 miles per hour but never ran faster than 7mph. Evolution would not produce these traits, either.

In summary: a brain that leaves 90% of its potential untapped would not evolve. But don’t let this fact stop you from making good movies that use this as a premise. Luc Besson doesn’t tell me how to do my job, so I won’t tell him how to do his.

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A Journey Through Plant Evolution at the Lincoln Park Conservatory

I recently spent some time at the beautiful Lincoln Park Conservatory. It is very hot and humid in the greenhouse, which may not have been the most obvious choice on a day that was already 88º outside. Nevertheless, I thought it would be a good way to talk about the evolution of plants. My specialty in biology is animals, but I have always loved the story of plant evolution. Like all other major groups of life on Earth, plant life began in the water. Early plants were very reliant on water, but plants became less and less dependent on water as they evolved. In the water, life is easy. Dehydration is not a problem. Nutrients can be absorbed directly out of the water into the cells. The water will carry sperm for reproduction and disperse the offspring. Life in the water is good, but there was a lot of space to grow on land.

The Lincoln Park Conservatory is a great place to go. A cooler day is better.

The Lincoln Park Conservatory is a great place to go. A cooler day is better.


One of the first types of plants to live on land were the liverworts. They are very small, with leaves that lie almost flat on the ground. Liverworts have no ability to draw water up out of the ground, as later plants are able to do. As a result, they cannot grow very tall and must be damp all of the time. They cannot survive or reproduce without being wet.

Liverworts are one of the first plants to live on land.

My favorite room contains the primitive plants: ferns, moss, liverworts, and cycads.

My favorite room contains the primitive plants: ferns, moss, liverworts, and cycads.


Like liverworts, moss also cannot draw water up into their bodies. Are able to grow a little bit taller than the liverworts because they grow in dense mats that can trap water between individual plants. This allows them to grow up to about four inches tall.

Mosses do not dry out as easily as liverworts, but they do rely on water for reproduction. The male sperm must swim through the water to find a female plant.

Like an idiot, I forgot to take a picture of moss. This one form will have to do.

Club Moss

Club moss are sometimes called “ground pines” because they can resemble pine trees, but they are neither pines nor moss. Modern club moss usually only grow to be a few inches tall, but during the Carboniferous period, when they were the dominant land plant, they grew as tall as modern trees.

Club moss are one of the first type of plants to have vascular tissue, which lets them draw water from the ground up into their bodies. This adaptation is of unparalleled importance for plants on land. For this reason, club moss were one of the first types of plants to be able to grow more than a couple of inches tall. Without vascular tissue, a plant more than an inch or two has no way of getting water to the upper part of the plant. Plants don’t need very much to live, but access to sufficient sunlight is one of their main requirements. When all of the plants around you are only two inches tall, a plant that can grow to be several feet tall or taller has an enormous advantage when it comes to getting sunlight. You can grow taller than your neighbors and spread out to get all the sun you want.

Club moss (not moss). Image from

Coal is made of fossilized plants from the carboniferous period. The majority of coal is made up of ferns and club moss. Sometimes coal preserves the structures of the plants it was made from and we can use the coal fossils to learn about ancient plants.

A thin section of coal clearly shows the features of the stem of an ancient plant (in cross-section). Image from


Evolutionarily speaking, ferns are slightly newer than the club moss. Like the club moss, ferns are have vascular tissue (so does everything else from here on).

Compared to most other plants, ferns grow sideways. The stem lies horizontally underground, and the fronds grow up out of the ground from it. When you see a cluster of fronds sticking up together, they are usually from the same plant.

Fern frond

Fern frond

Structures on the underside of the fronds, called “sori,” contain spores. These capsules break open, releasing the spores, and new ferns grow where the spores land.

Sori are clearly visible on the underside of fern fronds. These contain spores.

Sori are clearly visible on the underside of fern fronds. These contain spores.


Cycads look superficially like palms, pineapples or yuccas, but is not closely related to any of them. They were one of the dominant types of plants during the mesozoic era — the age of the dinosaurs.

Cycads were among the first plants to use pollen in reproduction. Pollen is produced by the male structures on plants, and is responsible for carrying sperm to the ovule in the female structures on other plants. Unlike the earlier plants, which require water for the sperm to swim through, pollen is carried by the wind. This is great for plants that live away from water and want to be able to reproduce with individuals that are far away. The problem is that it is fairly inefficient. Plants whose pollen is carried by the wind need to produce vast quantities of the stuff in order for some of it to get to other plants. I grew up in New Hampshire, where there a lot of white pine trees (which are not cycads, but also reproduce with wind-borne pollen). I got up many a morning to find my car completely covered in yellow pollen. All of that pollen that didn’t end up on the right part of the female plants is wasted energy.

Cycads were also among the first plants to have seeds, instead of spores like the older plants. Spores are fine, but they cannot travel over long distances or lie dormant for a more opportune time to sprout. A seed contains the plant embryo as well as nutrients to keep it alive for months or years. If a spore happens to land on the back of a bird on its way to the other side of the country, the embryo inside may not survive the trip because its mother didn’t pack it lunch. An embryo inside a seed will survive the same journey because it is surrounded in an oil-rich substance called “endosperm.” When we eat nuts, it is the endosperm that we are after.

Cycads can superficially resemble pineapples, yuccas or palms, but they are not part of the same group.

Cycads can superficially resemble pineapples, yuccas or palms, but they are not part of the same group.

Flowering Plants

Flowering plants became the dominant plants of the world during the late mesozoic, and today account for the majority of plant species.There are over a quarter million living species of flowering plants, compared to only about 12,000 species of fern, and fewer than 10,000 species of liverwort.

The flowering plants have two evolutionary advancements that allowed them to be so successful: flowers and fruit. These allow plants to solve two big problems in the area of reproduction.

Flowers represent an exchange of goods and services between plants and animals. Big, colorful, aromatic flowers are nature’s equivalent of an “eat here” sign. Flowers produce sugar-rich nectar that animals like ants, butterflies, birds, and bats like to eat. While these “pollinators” are eating the nectar, they get covered in pollen. When they go to the next flower, they drop some pollen off and pick up some more. This results in animals carrying pollen directly from one plant to the next, with very little waste. Remember all that energy that earlier plants wasted trying to pollinate my car? Flowers allow plants to use their energy more effectively. The energy this saves over relying on wind pollination is part of why flowering plants are so successful evolutionarily.

Flowers attract certain animals, which carry pollen between flowers, helping the plants reproduce.

Flowers attract certain animals, which carry pollen between flowers, helping the plants reproduce.

Spreading seeds is another problem for plants. If seeds just fall off the parent plant and onto the ground, some will roll away or get kicked away. The others will sprout right next to their parent and compete for the same nutrients and light. This will reduce the success of both the parent and the offspring. Some (but not all) flowering plants produce fruit to solve this problem.

Fruit is a sugar-rich substance that is easy to get eat, which surrounds the seed, which contains an oil-rich substance that is protected by a hard shell. In human terms, the plant “wants” you to eat the fruit, but does not “want” you to eat the seed. If you eat the seed, you are eating the tree’s offspring. If you (or another animal) eat the fruit, there is a good chance that you will swallow the seeds by accident. The hard shell protects it from being broken in your mouth or digested in your stomach. After eating the fruit, you (or whatever animal) will walk or fly away and eventually deposit the seeds far away in a nutrient-rich pile of fertilizer.

Flowering plants are better at life on land than any other plants. They can draw water and nutrients out of the soil through their roots and vascular tissue, and they are very good at reproducing and spreading their offspring without the aid of water. This is why they are beating all of the other plants.

Cladogram showing the evolutionary relationships of the plant groups and major evolutionary advancements.

Cladogram showing the evolutionary relationships of the plant groups and major evolutionary advancements.

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The Evolution of Flight

Out of several thousand species of birds, almost all of them can fly. They all have the ability to fly because they evolved from a common ancestor that could fly. Bats can all fly because they evolved from a common ancestor that could fly. But why can both birds and bats fly? Did they evolve from a common ancestor that could fly? While they did evolve from a common ancestor, this ancestor could not fly. How, then, are both birds and bats able to fly?

In biology, there is a concept called “convergent evolution.” Some types of organisms have similar traits because they evolved from a common ancestor that had those traits. With only a few exceptions, all mammals, amphibians and reptiles (including birds) have four limbs — two arms/wings and two legs. This is because these three lineages all evolved from a common ancestor that had four limbs. Similar traits that are due to common ancestry are called “homologous traits.”

Other types of organisms have similar traits but did not evolve from a common ancestor that had those traits. Fish and whales are a classic example of convergent evolution. They both have a tail fin that propels them through the water, forward fins that help them steer, a fusiform body that makes them hydrodynamic, and a dorsal fin that keeps them stable.

The dolphin and fish share many traits that facilitate an aquatic life. Image from

But there are more differences than similarities. Here are a few:

  • The tail fin of a fish is oriented vertically, whereas the tail fin of a whale is oriented horizontally
  • Fish lay eggs, whereas whales give live birth
  • Baby fish are fed by a yolk sack in their egg, whereas baby whales are fed from mammary milk
  • Fish use gills to extract oxygen from the water, whereas whales breathe atmospheric air
  • Fish are cold-blooded, whereas whales maintain a high body temperature.
  • Fish have scales covering their skin, but whales do not.
  • Whales have typical mammalian wrist and finger bones inside their pectoral fins, but fish do not.
  • Whales have hair, but fish do not.

Whales do, of course, share a common ancestor with fish, but this common ancestor is not the reason that whales have their aquatic adaptations. The ancestors of whales first evolved into a terrestrial life, then evolved back into the water, much later in life.

When two or more different types of organisms evolve a similar trait independently, these traits are called “analogous traits” and the process of evolving these analogous traits is called “convergent evolution.”

Off the top of my head, I can think of nine independent evolutionary origins of flight — that is, nine separate events of convergent evolution. There are probably more that I don’t know about. Let’s start with the three best fliers that are currently alive: Birds, bats and insects.

Birds and bats are both tetrapods, so they are stuck with four limbs. They both use primarily their front limbs for flight, but they do it differently. Bird hand and wrist bones are fused together to make a short, stumpy end bone. Feathers produce the area required to produce lift.

The bones of a bird wing. Image from

When birds are in flight, they keep their legs and feet tucked out of the way so they do not interfere with flying.

Canada goose in flight. Note that the legs are not used in flight. Image from

Bats have a membrane of skin that stretches between their arms and legs that help produce lift. The legs and feet of bats are very important for flight.

Bat in flight. The legs are important in forming the wings. Image from

Bats have elongated fingers that make up most of the wings. They use skin that is stretched between their fingers to create the area required to produce lift.

The arm bones in the bats and birds are homologous to one another, but their wings are the result of convergent evolution.

Insects have six legs and two pairs of wings. Insect wings are inflexible, except for where the connect to the body; a little bit like the oars on a boat. There are no bones or muscles inside the wings. Birds and bats have aerodynamic bodies that allow them to pass through the air efficiently. Some insects, like the dragonflies, have aerodynamic bodies, but bees and beetles do not.

Dragonfly. Image from

The pterosaurs were not technically dinosaurs, but they were close relatives. Modern birds, which are dinosaurs, are not direct descendants of the pterosaurs, but birds are more closely related to the pterosaurs than they are to bats. Despite the closer genetic relatedness, the pterosaurs flight ability resembles bats more than birds in a variety of ways. First, they did not appear to have had feathers. Instead, they probably used a membrane of skin to form their wings much the way bats do.

Bats use fingers 2-4 (index through pinkie) for flight, and finger 1 (the thumb) for limited gripping. Pterosaurs only had four fingers, and only finger 4 was used for flight, whereas fingers 1-3 were used for gripping.

Pterosaur wing. Image from


Other, lesser fliers:

These are animals that fly sort of like a paper airplane. They cannot propel themselves once they are in the air — they have to jump to get their initial momentum. But once they are in the air, they can control their direction and create an air foil to slow their falling. Humans can do this with the aid of a wingsuit:

Flying squirrels: A little bit like bats, flying squirrels have a membrane of skin that stretches between their front and rear legs. This allows them to glide over longer distances than they would otherwise be able to jump.

Flying squirrel in flight. Image from


Flying lizards: Although the word “dinosaur” literally means “terrible lizard,” lizards and dinosaurs are completely different types of reptile. Flying lizards in the genus “Draco” are not very closely related to the flying dinosaurs. The flying lizards are very unusual because they do not use any of their four limbs for flying. Instead, they are able to spread out their ribs to form fairly immobile wings which allow them to glide for short distances.


Flying dragon. Image from

Flying fish: Flying fish are much better at flying than you would expect. They use their tail to get out of the water and get speed. Once they are in the air they can glide for fairly long distances. If they want to increase their speed, they can put their tail back into the water and give themselves another push. This makes them the only glider that I know of that can add energy to their glide without landing.

Flying Fish. Image from


Flying frogs: Like bats, flying frogs create “wings” by stretching skin between long fingers. Unlike bats, the “wings” of the flying frogs are limited to their feet, and do not include any skin on the arms or legs.

Flying frog in flight. Image from

Flying snakes: To people who are afraid of snakes, nothing sounds more horrifying than snakes that can fly. But don’t worry — the flying snakes are the worst flyers of the group. They are able to flatten out their bodies to create a very minimal air foil. Their “flight” looks a lot like jumping or falling, but research has shown that they are able to steer themselves in the air. It may not seem like I should have included these in a list of things that evolved to fly, but remember that everything that evolved to fly had to go through many stages of flying ability. In the first stages, the animals would have just been jumping. In later stages, they would have a rudimentary ability to glide and navigate. For this reason, I firmly consider these snakes to be an example of incipient flight.



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