Chicago’s Field Museum of Natural History: Evolving Planet

The Field Museum of Natural History was founded in 1893 as the Columbian Museum of Chicago; the building was part of the 1893 Columbian Exposition (read “World’s Fair”). It is devoted to just about everything that has to do with our world and our place in it. It’s located in what’s called the “Museum Campus,” which includes the Shedd Aquarium and Adler Planetarium, right across the parkway from Soldier Field, on the lake at Roosevelt Road (12th Street). And it’s huge — it covers at least a full city block, with three floors devoted to exhibitions and a fourth to offices and collections (which are also housed throughout the Museum, behind the exhibits.) I’ve been going there for more years than I’m going to tell you, save to note that as a small child, perhaps five or six, I always wanted to see the “stuffed animals,” housed in reconstructions of their natural habitats; it wasn’t until later, when I began to share my father’s interest in ancient history, that I started looking at the Egyptian and American Indian exhibits.

Evolving PlanetGiven the size and scope of the Museum’s collections, I’m going to focus on one relatively new exhibit, “Evolving Planet.” It’s about what it says it is: the story of Earth, beginning perhaps half a billion years after it formed, and the plants and animals that have come to occupy it.

The exhibit opens with wall labels explaining, first, what scientists mean when they use the word “theory,” and the status of evolution as a scientific theory and the best way we have to describe the relationships among living organisms.

Then, immediately, one is led to a large animation of the early Earth — volcanos erupting, meteors crashing, and, finally, all the water vapor in the atmosphere (which was at the time unbreathable) raining down to form the oceans. This section poses the question of where organic compounds formed, noting the two major theories: one, they formed in deep sea vents where superheated water loaded with minerals escaped the Earth’s mantle into the newly formed oceans; or, second, they came in as passengers on the multitude of meteorites that crashed into the Earth’s surface. (I have one objection here: these are presented as an either/or proposition, but just a little bit of thought leads to the conclusion that they are not mutually exclusive.)

And then, life. The signage points out that scientists aren’t sure how it happened that those molecules organized themselves into living organisms, but it shows the evidence that we have that they did, starting with traces of carbon in fossil rocks. We are now in the world of prokaryotes, primitive single-celled life forms that are still with us (and outnumber the rest of us significantly): think bacteria.

And then (and again scientists aren’t sure exactly how it happened, just that it did), some cells began to engulf other cells, which were not digested but took up residence as mitochondria and other organelles, with their own DNA. (Another puzzle: no one is sure how DNA formed, only that it did.) And now we have prokaryotes, the group of organisms that includes amoebas, fungi, elephants, and us. Another thing was happening at the time that was to prove vitally important to the spread of life on earth: some organisms began photosynthesizing, taking in water and carbon dioxide and, by means of chlorophyll and other pigments, producing sugars for energy and oxygen as a waste product. This free oxygen, which hadn’t existed until then, spread through the oceans (incidentally forming vast layers of rust as it combined with the iron molecules in the water; today we know these layers as “banded iron formations”) and then leaking into the atmosphere, where it not only made the atmosphere breatheable but formed the ozone layer, which filters out the most harmful of the sun’s rays and would eventually make the land habitable.

And that’s the first three billion years of life on earth. Now we are about the enter the Cambrian, when things really took off.

The first innovation in this brave new world with breatheable atmosphere and shielded from the sun’s harmful radiation was the life moved into the shallow seas and produced multicellular organisms — the first plants and animals. (At this stage, there’s some debate about which were which.) I should point out that, somewhere along the line, living organisms discovered — or invented — sex, which opened up a broad range of possibilities. The exhibit explains the advantages and disadvantages of both asexual and sexual reproduction. (I should mention, although it’s not part of the exhibit, that at the beginning, sexual reproduction was a free-for-all: the regulatory genes that insure that fertility is limited to organisms of the same species hadn’t occurred yet, so basically, there was no such thing as a species.) There’s a small three-dimensional exhibit that shows reconstructions of some of the first multi-cellular organisms. They aren’t anything like what we have today, for the most part.

cambrian seaAnd then the Cambrian Explosion: this is the period of about a hundred million years when all the types of animals we have today originated, from sponges to arthropods to vertebrates. There’s a large, three-panel animation mounted on the wall that shows the Cambrian sea, with various animals moving through. Some of them are quite weird, some are fairly well-known, such as trilobites.

And then to the Ordovician and Silurian. The exhibit details the evolution of fishes, first the jawless fishes and then fishes with jaws, and from skeletons made of cartilage ( sharks, rays, and skates) to “bony fishes” — pretty much every other kind of fish. And then a display showing a reconstruction of Tiktaalik, thought to be the first fish that regularly came up on the land. The exhibit notes that the pectoral fins of Tiktaalik have a series of bones that are the same bones we have in our arms. And it’s during the Silurian that plants and animals moved onto land. There are explanations of how they made that breakthrough, as nearly as we can reconstruct it, and charting the development of, first, mosses and ferns, which were pretty much restricted to damp, marshy areas, and then vascular plants, which were able to move into drier areas, and then actual trees — cycads, ginkgos and conifers. (Fun fact: seeds originated about 200 million years before flowers.)

The exhibit then goes one to show the rise of amphibians (which for some reason Museum staff insists on calling “primitive tetrapods (‘amphibians’)”) and reptiles. There were an amazing variety of reptiles, and there are examples of each group. We’re now into the Permian period, which ended with the Permian Mass Extinction, which wiped out about 95% of the animal life.

(The exhibit does note the mass extinctions that occurred periodically — all five of them — and gives probable causes.)

Daspletosaurus_Field_MuseumAnd now, the part you’ve all been waiting for: dinosaurs. The Hall of Dinosaurs is really impressive — almost the entire east side of the second floor of the Museum is a large — and I mean really big — room containing fossil skeletons of various dinosaurs. (A note: as of this writing, March 2018 — the world-famous Sue is off exhibit while a new area is being prepared for her as part of this exhibit. Her place on the main floor is being taken over by an even larger fossil skeleton from South America.) This portion is very well organized, with examples of the various kinds of dinosaurs laid out in a way to clarify their relationships, including a very instructive section on the origin of birds — the only surviving dinosaurs. There are also a couple of small exhibits noting the development of plants, including the appearance of the first flowering plants about 144 million years ago. This section ends with another mass extinction which marks the close of the Mesozoic Era and the obliteration of the dinosaurs (except for birds). I could wish that more attention had been paid to the origin of mammals near the beginning of the Age of the Dinosaurs. They arose from a different group of reptiles and were around pretty much the whole time.

Barylambda faberiHowever, mammals come into their own in the next section, the Cenozoic Era, which saw not only the rise of mammals but the spread of flowering plants, the continued evolution of birds — and ultimately, us.

Once again, the timelines are neatly laid out, with a number of fossils that show the evolution of mammals from tiny little creatures about the size of your finger to such giants as ground sloths (the fossil skeleton of that one is huge), with a section noting the various groups — rodents, carnivores, hoofed mammals, primates, lagomorphs, and the like.

Ultimately, of course, we wind up with the appearance of hominids and, eventually, humans. This is a rather small section, but contains a cast of the skeleton of Lucy, along with a reconstruction, as well as a reconstruction of the Turkana Boy, with comparisons between early and modern humans.

The exhibit ends on a sober note, with a large display on the “Sixth Mass Extinction”, which could be happening right now.

A few notes:

The documentation of the exhibit is extensive, with fossils from the Museum’s own collection, supplemented by casts of fossils from other museums (although for the dinosaurs, at least, over 90% of the fossils are genuine).

Consequently, there is a wealth of detail in each section that fills in the areas around the major elements.

Each section begins with a vertical depiction of the geologic timeline, showing where you are. There are also dates set into the floor (i.e., “535 million years ago” at the beginning of the Cambrian).

There are also small signs at the beginnings of the sections noting the location/arrangement of the continents — because, after all, they’ve been moving around for the whole four billion years.

There are animated videos showing how various elements of life on earth came to be and how we found them — for example, one on “How to Become a Fossil.”

There are periodic videos featuring interviews with specialists in various areas about how they work and how they reach their conclusions.

Interspersed throughout the exhibit, at the appropriate places, are paintings by Charles Knight, who was commissioned to recreate scenes from various stages of the evolution of life on Earth.

Given the location of the Museum, it’s perhaps no surprise that there is a discernible Chicago emphasis in some sections — including a walk-through of the lush forest that covered the Chicago area a few million years ago.

This is, by necessity, a somewhat abbreviated tour through the exhibit: it covers most of the second floor of the east wing of the Museum. I recommend that you leave yourself at least a couple of hours to view it. Happily, there are benches placed at various intervals, so you can sit down for a bit before you dive into the next period.

About Robert Tilendis

Robert M. Tilendis lives a deceptively quiet life. He has made money as a dishwasher, errand boy, legal librarian, arts administrator, shipping expert, free-lance writer and editor, and probably a few other things he’s tried very hard to forget about. He has also been a student of history, art, theater, psychology, ceramics, and dance. Through it all, he has been an artist and poet, just to provide a little stability in his life. Along about January of every year, he wonders why he still lives someplace as mundane as Chicago; it must be that he likes it there.

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