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B1G Power Poll Week 11: Major Evolutionary Milestones

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You really gon’ learn today

Zina Deretsky/National Science Foundation

So for those who have been following my illustrious “career” here at Off Tackle Empire, you’ll know that each year I do one big scientific themed Power Poll, and in fact my first official piece was this Dinosaur-themed power poll. Since then, I followed that OTE career start with power polls dedicated to non-dinosaur extinct animals in 2016, marine tetrapods in 2017, the geologic time scale in 2018, semi-aquatic tetrapods in 2019, and crocodilians in the year that we’ve all forgotten. Well, this piece I will be considering my scientific Power Poll Magnum Opus (up until this point). I want you all to know that I put in a comical amount of research time into this piece for something that gives me literally nothing the invaluable love of Off Tackle Empire readers.

First, some background on myself, as these write-ups are getting bigger and bigger and I may use them on my CV one day as part of my SciComm. I am a PhD candidate (woooo) in vertebrate paleobiology (at USC. Yes the Pac-12 sucks). My research is focused on the locomotion changes in the evolutionary transitions where by which land tetrapods evolved to go back into aquatic environments (Tetrapod, descendants of walking fish: vertebrates with four legs [even including snakes and other things which just lost their legs because evolutionary categorization is based on shared history]). My study animals are things like whales, seals, manatees, crocodiles, sea snakes, and sea turtles, extinct marine reptiles like mosasaurs, plesiosaurs, and ichthyosaurs <— these are not dinosaurs, though they lived alongside them, and a whole manner of semi-aquatic animals.

I am many things— a paleontologist because I deal heavily with fossils, a functional morphologist and biomechanist because I deal with locomotion, an anatomist because anatomy is the foundation of all that I study, but most of all, I think, I am an evolutionary biologist. I just love evolution and I selected my undergraduate major degree at Rutgers because it had the word “evolution” in it. So when thinking of a power poll to write for this year, I thought, “why not take people on a journey through life history and its major moments?” I always found thinking about evolution to be humbling and it helps keep the world in perspective when it gets tough, the same way thinking about geologic time does. So without further ado, behold my OTE Power Poll Magnum Opus, fourteen major evolutionary milestones and events that have changed the course of life on our planet. Disclaimer: All of these are important and “ranking” them based on our Big Ten teams was, as it always is, hard.

1. Ohio State— Land to Air Transition in Vertebrates

The evolution of powered flight in vertebrates occurred three times. The first was in pterosaurs (animals like pterodactyl and pteranodon) which are closely related to dinosaurs, but not dinosaurs. Pterosaurs evolved flight in the Triassic Period and they built their wings by elongating their 5th digit (pinkie) and attaching a skin membrane from it to their body. Next were birds, which are dinosaurs, and birds evolved in the Late Jurassic. Birds make their wing by reducing and fusing the metacarpals and fingers and having rigid asymmetrical flight feathers coming off the arm. The third land to air transition occurred in bats which likely evolved in the Eocene, about 50 million years ago. Bats of course build their wings by elongating four out of their five fingers and stretching skin over them. These independent evolutionary emergences of wings is a phenomenon known as convergent evolution. All these ways to create a wing reflect Ohio State staying at the top of the Big Ten regardless of personnel, coaching, and player changes. A wing is a wing, and an Ohio State team is an Ohio State team. The evolution of flight is really remarkable for vertebrates because flying vertebrates just dominate their respective ecological niches. Bats are the second largest order of mammals alive today (after rodents) and birds are the second most diverse and speciose vertebrates alive today (after fish). Flight equals evolutionary advantage. That ecological domination matches Ohio State where there really seems to be no major competitor for it in this conference.

2. Michigan— Sea to Land Transition in Vertebrates

This transition, famously captured by the “walking fish” was significant. For the first time, large animals with internal skeletons emerged onto land, able to fight both the sun and gravity, escaping crowded water sources that have been teeming with life since the Cambrian explosion. These walking fish are part of a family of fish called lobe-finned fishes which includes coelacanths and lungfish. Fun fact, a lungfish is more closely related to us than it is to a shark. And yes, we are all fish. One of the most significant adaptations that some of these newly walking fish underwent to be able to survive on land away from water is the amniotic egg which mimicked a nourishing aquatic environment by having water inside the egg. A placenta is the same thing, just without a shell, and internal. This feature is shared by reptiles (birds included) and mammals. Not all walking fish would develop an amniotic egg, as amphibians are still reproductively tethered to the water. I think this transition captures Michigan because however Michigan flounders like a fish out of water, they are still all around pretty impressive and have a lot of potential this year, the same way those early tetrapods had the potential to evolve into amphibians, reptiles, and mammals.

3. Michigan State— Land to Sea Transition

The land to sea transition is really cool because these vertebrates, after spending a few tens of millions of years on land literally said, “we have to go back,” and took the advantages they gained from living on land and evolved back into aquatic environments and came to dominate them. Some of these advantages are physiological, for example breathing air is more efficient than breathing through gills. In the modern, representatives of this transition include animals like whales, manatees, and pinnipeds (seals, sea lions, and walruses) and a slew of semi-aquatic animals like hippos, platypus, crocodiles, otters, marine iguanas, sea snakes, and sea turtles. As well as numerous extinct groups, mainly marine reptiles, like mosasaurs, plesiosaurs, ichthyosaurs, marine crocs and tons more. These groups all did this independently starting in the Permian with small semi-aquatic reptiles called Mesosaurs, but really taking off in the Mesozoic with ichthyosaurs and plesiosaurs, and of course more recent invasions with marine mammals. I feel this evolutionary transition represents Michigan State who this year returned to the company of the top B1G bois after being out of it for a few years.

4. Wisconsin— Land to Air Transition in Insects

Biggest insect ever was a flying insect. Meganeura.

This is the evolutionary transition that gets ignored in favor of the more charismatic version found in vertebrates (which I aptly categorized as Ohio State for continuity because no one ever cares about the top B1G West team). Flight in insects was the first biological flight, and likely evolved in the early stages of the Carboniferous (360-289 mya). Flying insects dominate animal diversity today, but again, get ignored because people don’t love them. Insect flight actually has a really neat evolutionary question associated with it. What exactly is an insect wing? In pterosaurs, bats, and birds these wings are modified arms and this is very obvious. But insects have 6 legs (spiders and centipedes are not insects). Did they have 8 legs and two turned into wings? No, they couldn’t have because non-flying insects have 6 legs too. We don’t have fossils of the first flying insects, nor do we have great transitional fossils. The first flying insect fossils we have are of fully realized flying insects. So again, what is an insect wing? Well, without getting to bogged down in insect anatomy, thanks to developmental biology we think insect wings probably evolved via this “dual module” where symmetrical pieces of the thorax and lateral elements of the body worked in tandem/fused to form the wing. So bugs fly with their body. This fits Wisconsin because when the Badgers have won this year, they absolutely bodied most teams, winning by 3 or more touchdowns in their last 3 games. (citations 1, 2)

Image of a Tweet that says: I hate flying insects man, you can fly FOR FREE. You could fly to any holiday destination of your choice but here you are in my face.
One of my fav Tweets ever.

5. Iowa— Plants Invade Land

Plants invading land is a massive milestone and you can thank their invasion for your existence. Plants provide the biotic bedrock of terrestrial life on earth. Without land plants and the soil and sedimentary stability they create our planet would look very different. They also serve as the base of the food chain and produce oxygen (but algae produces more). Plants invaded land in the Ordovician Period (485–444 mya) and the oldest land plant fossils resemble the spores of modern liverworts. Their origins were humble, likely evolving from the algae at the edges of shallow and still bodies of water gradually becoming more resistant to desiccation and drier conditions before becoming fully untethered from the water, conquering the limitations of gravity, and exploding into the amazing diversity of plants we have today which exist globally, even in the harsh interiors of continents, thousands of miles from any ocean. However, this critical transition gets ignored in favor of the animal ones. It was important and, sure, we all “know” that, but let’s be honest, everyone underestimates and underappreciates plants and their evolution. Is that Iowa? I don’t know... because I don’t care about Iowa anymore. I take Iowa for granted. (Citation: 1)

6. Penn State— Insects Invade Land

Truman, 2019, Current Biology

Another evolutionary milestone where vertebrates get more love (for good reason), but insects did it first and did it very well. They were the first animals to detach themselves from aquatic environments and diversify into empty ecological spaces on land. Insects, or members of Insecta, are a legitimate evolutionary classification. They are arthropods categorized by having 6 jointed legs, most have one or two pairs of wings, and a head, abdomen, and thorax (spiders and centipedes are not insects). Insects are the most diverse group of animals, they represent more than half of known life, and they dominate the terrestrial realm. Insects evolved from aquatic arthropods right around when plants invaded land about 480 million years ago in the Ordovician Period. They existed on land for nearly 100 million years before vertebrates would emerge from the water onto land (and put them in their place). Insects are huge in numbers, big winners of evolution (if evolution had winners), but most people hate them. That’s Penn State. (Citation: 1)

7. Purdue— Oxygenic Photosynthesis

The evolution of oxygenic Photosynthesis is a major evolutionary milestone not just for life, but for the planet because it changed the world of early life, and thus later life including us, and literally changed the composition of the Earth’s atmosphere. There is debate when precisely major oxygenic photosynthesis evolved, but using the geochemical rock record, we know that 2.4 billion years ago there was a huge surge of oxygen into the atmosphere as captured by banded iron formations. This oxygen injection was caused by the evolution of cyanobacteria, photosynthetic prokaryotes. Cyanobacteria’s revolutionary metabolic process really messed up the world as oxygen was (and is) toxic to the anaerobic (not needing oxygen to metabolize) prokaryotes at the time which had dominated life since it evolved a billion years prior. Purdue is often that team that messes up things as we know it and while they did not knock down Ohio State this past weekend, they still beat Iowa and Michigan State definitely shuffling the prevailing narrative behind the B1G East.

8. Minnesota— Bioturbation

Näkki et al. 2017

The evolution of bioturbation is a big deal and that’s unfortunate because it’s likely that you won’t care about it. Before I delve into what this is, picture a planet devoid of life. The rock on the surface weathers and turns to sediment and that sediment settles in various sinks, only being moved by mechanical environmental processes like tectonics, wind, and water. At the onset of early animal life, suddenly it was life like WORMS and other burrowing things that were also was moving and disturbing sediment. This would allow gases and liquids that would never normally reach these layers to penetrate and mix the sediment completely changing the geochemistry. This would set the groundwork for so much of the life that would follow, for example plants and other organisms that rely on nutrient cycling in soils and sediments. Earth is the only planet that we know of where life actively moves around rock. This is actually a big deal/a big deal to a certain subset of nerds but it’s hard to convince people of that. Guys, Minnesota almost beat Iowa. They’re 3rd in the B1G West! Notice them! Also Gophers burrow. Burrowing is bioturbation.

9. Illinois— Evolution of Flowering Plants

Photograph: Hervé Sauquet & Jürg Schönenberger.

Believe it or not, flowering plants, also known as angiosperms, have not always been around. Flowers evolved to better protect the seed of the plant and to facilitate fertilization and other aspects of reproduction. Angiosperms evolved in the Early Cretaceous (a good bit earlier than when T. rex and Triceratops showed up on scene) and not too long afterwards would spread across the world to replace conifers as the dominant plant thanks to their successful new reproductive strategy. And of course what would a flower be without it’s close relationship to pollinators like insects for which they started a whole new ecological role for? Like the early evolution of flowering plants, Illinois seems to be starting to bloom under Bret Bielema the way those first flowers started out. Bert is nurturing the long dormant seed that is Illinois football and they finally have a pulse. They probably won’t grow into the magnificent, refined, and efficient flowering plants of today, but is still an impressive innovation nonetheless.

10. Rutgers— Origin of life

Henning Dalhoff/Science Photo Library

Arguably the most major evolutionary milestone on this list, the one that enabled all the others to take place (yes, that’s a reference to the Birthplace of College Football, I had to spell it out). The origin of life likely occurred at least 3.5 billion years ago, which is about a billion years after the formation of the Earth 4.6 billion years ago. Life is just chemistry and it’s not that ridiculous a notion to think that 1 BILLION years of the existence of the chemical soup of a fresh planet would give rise to biological molecules like amino and nucleic acids and hydrocarbons. After life originated it did a whole lot of what we being biased to animals, plants, and complex life would consider “nothing.” However, life seems to have more recently found its groove in the broad eon we are currently in called the Phanerozoic (which started at the Cambrian explosion 541 mya) after inventing itself and doing nothing impressive for so long. It’s Rutgers. Rutgers is doing cool things now, like blowing out a Big Ten team, which is relatively recent compared to its long history in the sport of College Football.

11. Maryland— Cambrian Explosion

Credit: John Sibbick/Natural History Museum

The Cambrian Explosion (~541 mya) marks the point at which life, one could argue, started to resemble what we have today. At least in the water. It would be a strange, alien world, no doubt, but you would recognize worm-like things, predators swimming around the water column, bug-like things, shelled things, etc. The Cambrian Explosion is when the modern groups of animals evolved, including chordates which would give rise to vertebrates. The exact driver of the Cambrian explosion is unknown even though it is an event that changed animal life forever. It was likely a combination of geochemical and biological factors. Some have hypothesized an increase in Oxygen or the evolution of predators and vision. Either way, it happened and it spiraled into modern life despite starting out so alien. Just like in Maryland Football where one can recognize bits and pieces of a... football team... sure. (Citation: 1)

12. Nebraska— End-Permian Mass Extinction

This major evolutionary milestone is an extinction. And not just any extinction, but the most devastating mass extinction in life history. If that doesn’t sum up Nebraska’s futile attempts to reclaim its long past status I don’t know what does. This extinction was likely at least partially (but to a large extent) caused by millions of metric tons of carbon-rich sediments being set afire and combusted into greenhouse gases causing rapid global warming (heyyy...) by the Siberian Traps, a huge area of volcanic rock in Siberia, known as a Large Igneous Province. This volcanic activity that was on a scale that is truly unfathomable to humans raged on for 2 million years and resulted in the extinction of 90% of marine species and 75% of terrestrial species. It completely reshuffled which animal groups would come to rule in the wake of the extinction and knocked out many of the synapsid groups (the group that we, mammals, belong to) that dominated Paleozoic landscapes. The End-Permian Mass Extinction paved the way for the age of Reptiles and eventually dinosaurs. Thanks to Nebraska whose extinction has paved the way for different teams to dominate the B1G West.

13. Northwestern— Multicellular Evolution

A fossil of a 600 million-year-old multicellular organism displays unexpected evidence of complexity. Credit: Virginia Tech

Multicellular organisms evolved at least around 600 million years ago, possibly much longer ago, but either way it took a very long time for cells to begin working together at higher levels in comparison to the 3.5 billion years ago that life evolved. Humans, as one example, have 37 TRILLION cells that work together to form one organism and it is a remarkable evolutionary innovation. Multicellularity is hypothesized to have occurred when unicellular eukaryotic cells started to form clusters and the clusters which survived based on their collective traits would persist until eventually a true collective happened where cells could no longer survive alone. I don’t really know why this is Northwestern, but it was on my list of evolutionary milestones and the last one I wrote up. I’m more trying to be academic than accurately connect these concepts to a team, heyyy wait a minute. (Citation: 1)

14. Indiana— Evolution of Humans

Chip Clark, Jim DiLoreto, & Don Hurlbert/Smithsonian Institution

So the first human-like (walking on two legs) apes evolved about 7 million years ago, but these apes weren’t really showing signs of our modern intelligence until around 2 million years ago. In modern humans, our adaptability, technology, and ability to modify the life and planet around is unparalleled through the history of life, truly. You’re probably wondering why the evolution of our species is listed last. I mean our species, Homo sapiens, is ~200,000 years old and look at what we’ve done.... look at what we’ve done. We’re fascinating animals, but there are some straightforward negative facts about what humans have done to the biosphere that are facts no matter how you try to justify them or pretend they’re not problems: agricultural land use and monoculture, habitat fragmentation, overhunting, overfishing, extinction, deforestation, plastic pollution and microplastics, toxic/radioactive environmental pollution and contamination, CLIMATE CHANGE, and... the pug. To name just a few. We blow. We had so much potential to not blow, but right now we just blow. Indiana is the epitome of blown potential this year. How did they start off ranked? They were so solid last year. What is going on?? Blown out by Rutgers. Geez, Indiana, get a grip.

Well, that’s all I got. This is 3,230 words, I don’t need to say any more. I should be writing!... something academically important.