Chapter 2
Get A Life
…
3.8 Billion Years Ago
After a little nap along the margins of the primeval shoreline, you walk with Peridot back to the time machine. She talks as she sets up everything. "As far as organic life on the planet Earth is concerned, we haven't the foggiest clue how it got started. Your scientists have been hard at work observing, hypothesizing, and testing anything and everything related to this mystery, but at the moment we can't say anything definitive. That being said, they have been amassing and connecting all sorts of puzzle pieces to the question of organic life's origins, and for right now, we have some… highly likely scenarios that we can explore. But to do that, we gotta get smaller!"
Opening up a new section of the holoscreen, Peridot places a finger along what looks like a computer scroll bar and pulls downward. Next thing you know, the view outside the window appears to be growing tremendously. Taking a cue from Peridot's words, you realize that she's shrinking the time machine!
As you reach microscopic size, Peridot takes the pod and flies it right into the seashore. You dive down, deeper and deeper, darker and darker, until it's nearly impossible to make anything out. After several minutes of travel, Peridot slows the time machine to a halt and flips on some headlights. You see what appears to be several large castles of rough-yet-polished stone. The water surrounding the pod is very still, but you feel the warmth radiating from these rocky structures. All around you are millions of small molecules, swimming around and or floating like suspended snowflakes.
"Organic life on Earth is made up of cells, which are these little tiny bags of matter that perform all sorts of functions, mainly keeping the organics alive. Given what we know about Earth life, the first organics were single-celled, but there's a very long road to get to something as complex as a cell. Scientists call this period of development 'abiogenesis': before life appeared."
Peridot drives the pod up to some early microbes. "These early bacteria can help you understand. By this time, 3.8 billion years ago, life seems to have already finished abiogenesis, and you can see all the end-results clearly with these little guys." She focuses the headlights directly on one of the bacteria, giving a good outline of all its internal anatomy. "Cells are made of organic molecules, which are chains of atoms. Our friend carbon, which we met after its creation from the first generation of stars, was the most important of these linked atoms, because it's the only one that can readily bond with other atoms to form organic molecules in the first place. And these chains can link even further together to form larger 'macro'-molecules, like sugars, amino acids, phosphates, and nucleotides."
Peridot points to the center of the bacterium, drawing your attention to the large stringy mass at the center of it. "Moving a step further, nucleotides, phosphates, and sugars combined make up the structure of DNA and RNA. It's thanks to these molecules that organics have the necessary blueprints to reproduce and make more of themselves! Ahh the miracle of life." Peridot beams, before motioning the time machine back towards the stone castles.
"I noticed you looking at those rocks. Those are alkaline hydrothermal vents. There are quite a few of them on your present-day Earth, deep in the oceans. Certain types of rocks from deep in the mantle interact with water inside the vents, causing it to heat up tremendously, after which it is exhaled through all those little holes along its surface. Thankfully, I've designed this time machine to be resistant to extreme temperatures, but I still can't help but feel the warmth. My temperature gage tells me the water surrounding us is 190 degrees fahrenheit. Well, an oven is much hotter, but still. Yeesh."
The pod zooms down towards the hydrothermal vents and is quickly surrounded by all sorts of floating molecules. "Earth scientists suspect that vents like these provided the ideal conditions to foster the building of organic molecules and eventually the first living things. Living cells need a constant energy flow of carbon atoms to sustain themselves, and you get just that in environments like these."
Peridot notices some small wiggly molecules floating about and sticking to each other, and she takes the time machine closer to them. "Ooh! Look! Phospholipids! These little cuties are made up of two parts: a head that is attracted to water and a tail that despises water. As you can see, these molecules will often seek each other out in the right conditions and form little bubbles. All the heads made up the outer wall, and the tails form the inner wall. If we turn to the little bacteria we saw earlier…" and Peridot moves the pod back to them "... we can see the importance of this process in abiogenesis. The phospholipids would have provided a safe home for all these forming organic molecules, and with a few more alterations, the first cells arose!"
Now the time machine is moving away from the hydrothermal vents and slowly cruises along the ocean floor, passing by countless varieties of bacteria. "The last step towards proper organic life was the ability to reproduce. Having mentioned DNA and its coded instructions, but I should also mention that those phospholipid bubbles we saw have the ability to grow by adding new phospholipids from the environment. But after a certain size, the bubbles can't get any bigger and they collapse down their middles, eventually splitting into two bubbles. You might see where I'm going with this. With DNA safely inside the proto-cells, copying itself as it does, there would come a point where the cell would need to split. This process would cause the DNA to replicate itself entirely, as would the rest of the cells component parts. Now, the DNA replication process isn't always clear cut, and mistakes get made all the time. These little changes in the DNA code, what we call mutations, can have little to major consequences on how the cell functions. Once this process started in the early oceans, evolution could begin, and thus, organic life could truly call itself alive."
Peridot sets a new date, "how exciting. Steven explained it to me best, 'everything always changes here on Earth. Nothing is still.' Evolution is a way that ensures that living things are always able to experiment and explore new possibilities. Organic life can be rigorously shaped by its environment, and shape its environment in turn. Certain ways of life can be so successful that they're copied by different organics again and again. And sometimes the most insignificant mutations can have cascading effects! Let's move forward and I'll show you what I mean."
…
1.8 Billion Years Ago
The time machine, still shrunk, reappears in the Earth's ocean, but it's still pitch dark around you. "Woops, I need to take us to the surface." Peridot comments, and as she moves the pod upwards, you notice that the reddish-black water has become a rich blue. Near the surface, Peridot stops the machine, and you can see sunlight sparkling through the waves above.
"For nearly 850 million years after it developed, organic life was anaerobic. That means that they didn't use oxygen in their daily functions. These bacteria and their relatives were able to survive just fine, all they had to do was eat the inorganic materials around them. But there was still a problem: even with a magnetic field protecting from solar winds, ultraviolet radiation was still an ever present danger to Earth life. The first life had to stay down very very deep in the oceans to keep themselves from dying."
The pod is surrounded by all sorts of microscopic organisms. "As you can see around us, that's no longer the case by now. And it's all thanks to the power of photosynthesis! Check out these bacteria!" Peridot grins as she motions both of her hands towards some of the single-celled creatures, who had a green tint to them. "It's a genius mutation: they take the energy from sunlight and use that to turn carbon dioxide and water into sugar, which gives the cell energy function! Not only that, but they release oxygen as a waste product. Remember the early atmosphere? All colored orange?"
You nod curiously, at which point Peridot jolts the time machine at the ocean surface. The sky has turned a familiar shade of light blue, and there are white fluffy clouds about. "All that oxygen had to go somewhere: the sky! Well… first it sank into the seafloor and rusted all the iron minerals there… but then it went to the sky! Earth's earliest atmospheres had no oxygen, but they had a lot of harmful methane and ammonia. The ever increasing flow of oxygen displaced much of this stuff down to safer levels, and later formed a thick blanket around the planet that we call the ozone layer, keeping most of the ultraviolet light from reaching the surface. Isn't that cool?! Organic life essentially changed the planet!"
Peridot took the time machine down into the ocean again. "All the anaerobic life that had previously been confined to the seas was able to reach higher and higher in the water until they covered the seas. Now that there was a ton of oxygen, some of the anaerobic life evolved into aerobic life, while the others had to find new environments to live. Evolution in action."
The two of you admire all the different bacteria from the window, but after a while a large shadow starts to loom over you. Your eyes grow wide in confusion. Noticing this too, Peridot turns the pod and comes face-to-face with the looming maw of a much larger single-celled creature.
"WAAHHHHHH!" Peridot screams as the time machine is consumed completely! The creature swims along as the two of you are trapped inside a soft-gelatin mass of stuff.
"Aww gross!" Peridot exclaimed, "... well… it's not like we're in any real danger anyway. Might as well take this situation as a convenience, since this organic represents a crucial part of my story." Leaning back, Peridot continues, "all of the Earth's life during the first 2 billion years was prokaryotic, meaning that their cells were relatively simplistic: mostly made of a mass of DNA at its center. But around this time, 1.8 billion years ago, the first eukaryotic organics evolved. This time, the cell was much more complex, with a nucleus at its center to house DNA, and multiple other 'organelles' that perform different tasks. You can see the nucleus inside our hungry eukaryotic friend here." You're able to make out the greenish sphere from beyond the window, along with some other more ovaline shapes alongside it, which you gesture to Peridot.
Smiling, she places a hand on your shoulder. "Good eye! Those are mitochondria, which give eukaryotic cells energy. Do they look familiar to you?" You turn back, squinting at the globular ovals for good measure. "Kinda look like bacteria, don't they? Well, you'd be right! It turns out that the mitochondria, one of the fundamental characteristics found in nearly all eukaryotic organisms, originated from free-swimming bacteria."
Peridot pulls out her screen, "as our voracious host has demonstrated, many single-celled organics eat by completely encapsulating others. Now, usually, the prey are digested, but at sometime before 1.8 billion years ago, one of these single-celled creatures ate a smaller bacteria. Instead of digesting it, the two learned to live together: the bacteria providing the larger host with an easy energy supply, the host providing protection for the little one. Following the generations, this relationship remained strong until the two could no longer live without the other! Talk about the perfect fusion! Garnet would be proud." Peridot chuckled happily, "from these emerged all eukaryotic organics on Earth, basically all of the most familiar kinds you know about, like plants, fungi, and animals, as well as other microbial things like amoebas."
You feel the time machine shaking, which causes Peridot to groan. "Ugh… we're humble travelers from the future and all we get as a 'hello' is stomach grumbles?! Where are this thing's manners?! Let's get out of here."
Peridot sets the timer again, and the time machine vanishes in a flash, leaving a very confused and upset eukaryote.
…
740 Million Years Ago
The time machine, now regular size, blinks into a drastically different landscape. There are enormous glaciers surrounding the pod, which has become partially submerged in a muddy snowbank. The cold is so intense that you feel the change inside the pod, and gusts of wind pound at the sides. The sky is intimidatingly cloudy.
Seeing you shiver, Peridot wraps an arm around your body as her gemstone begins to glow. "This should help. My gem can radiate heat. We won't be here for too long anyway, I just want to show you a very dramatic episode of Earth's history."
You feel the heat begin to work its magic and soon you're snug as a bug.
"The rise of oxygen in the atmosphere not only lowered the levels of harmful methane and ammonia, it also dropped carbon dioxide levels. Carbon dioxide is a greenhouse gas: it works like a blanket, trapping heat from the sun and keeping it on Earth, causing warming. So for the first few billion years, Earth was a toasty place. But with all this oxygen now crowding everything, the Earth's climate began to cool. Add to that a many millions of years of great forests of photosynthesizing marine algae, releasing even more oxygen! It got so bad that - at least once - the entire planet became covered in snow and ice. That's where we're at right now: 740 million years ago, Snowball Earth."
Peridot takes the controls and activates the pod's walking legs. Taking a cruise across the snowy fields, you see small frozen streams but no sign of the ocean.
"This was a very difficult time for life. Because Snowball Earth formed so quickly, many organics didn't have enough time to adapt to the changes, and they died off in huge numbers. That's a trend that you'll notice in the history of Earth life, as gradual changes in environmental conditions are much more manageable for living things to evolve with than sudden shifts like this. Those that survived were able to do so because they migrated to the furthest depths of the oceans, which were spared from the intense cold."
Hearing a strong rumbling sound, you cock your head to the side. "I hear it too, let's investigate." Peridot motions the pod forwards as the legs sprint across the landscape, only stopping once it reaches the edge of a glacial cliff-face. In the distance is a massive volcano, erupting and spewing thick clouds of ash.
"Ah, of course." Peridot comments, "Snowball Earth only ended because of a massive spike in volcanic activity. Volcanoes release carbon dioxide as waste products, and this change reduced the amount of oxygen and brought to Earth on a steady rise in temperatures. This melted all the glaciers and once again provided a planet that was safe for life to live on. Now the conditions were right for the next great change!"
…
508 Million Years Ago
The time machine appears at the surface of a vast lagoon, floating calmly in the water. The sun has just risen, and the sky is bathed in a calm pinkish-orange. You can definitely tell there is a change in the air, you feel it.
"After Snowball Earth, animal life evolved and diversified into a myriad variety of forms. Animals, like most plants and fungi, are multicellular: made of many cells. Multicellular organics have been around for a billion years or more, some prokaryotic, others eukaryotic, but animals were unique in that they're the only multicellular eukaryotes that move around by themselves."
Peridot takes the pod and descends below the depths, curving over the edge of a massive slope hundreds of feet high. "Be sure to take a good look, because life on Earth has gotten much more fascinating!"
Going down about 320 feet, you finally reach the seafloor and your sight is treated to a spectacle of colorful and diverse animal life. Stalked forms, free-swimming forms, crawling forms, burrowing forms: each one is weirder than the last, just barely recognizable as anything you've seen at the beach or aquarium. Peridot shares your enthusiasm.
"It's awesome. Animals as far as the eye can see! This time is known as the Cambrian Period and it marks the time when organic life became much more abundant, much more complex, and actually visible to the naked eye. No need for shrinkage here!" Peridot, takes the pod and hovers over a grove of strange, bug-like animals that resemble rolly-pollies. "These hardy little critters are called trilobites, cousins of insects and spiders. During this time, they evolved and became super common, probably the most common animals around! What makes them and many other animals so special is that they were the first organics to develop hard parts to their bodies. What we call skeletons!"
Peridot pushes a button on the holoscreen, which sends a small grabbing arm outwards. The arm picks up a trilobite as the others swarm away from it. Gently, the arm brings the squirming animal close to the window. "Pardon me little buddy." Peridot sheepishly smiles, "I need you for a second."
She gestures you to come closer to the window. "The first animals, like all early organics, had soft bodies that were often delicate. The first animals to evolve hard parts were worms that incorporated neighboring minerals into their growth, what we call biomineralization. These worms developed sharp teeth that they used to better grasp their squishy prey. As an evolutionary response, these prey animals all took to using biomineralization for themselves, creating sharp spines or hard shells for protection, or even stiffening rods to support themselves on the seabed. Before long, much of the animal kingdom had hard parts of some sort, leading to the evolution of major animal groups like the mollusks and the arthropods, the latter being the group that organics like this little trilobite belong to."
Peridot makes the arm release the little animal, which wiggles around in shock before swimming back down to the seafloor and burying itself.
"Many of the animals you see here belong to groups that have survived and diversified in the present day. But there are others that have left no living descendants today. Even if we know who their closest relatives are, they still defy expectations. Like, check out this one!" Peridot motions towards a great free-swimming animal that had been circling the area for a while, hunting for prey. It has two bulbous eyes on its head, tipped below with two grabbing arms lined with spines. The body is long with undulating fins all along its sides.
"Talk about alien… of course, I would know. Nehehe! This is Anomalocaris, and it is abnormal! It's a great predator, using those spiny arms to grab smaller, softer animals and bringing them to a circular tooth-lined mouth under its face. Not a way I'd want to go. Look at those eyes! Eyes are another big adaptation that became fully realized during the Cambrian. Originally developing as light-sensing spots, over time several lineages of organics modified their eyes by creating little depressions in their faces which allowed them to sense direction. Some added a pinhole to give proper image processing, and eventually lenses for clearer sight. You know, the first gems had eyes… we didn't have to go through all of that."
You shrug your shoulders, which causes Peridot to giggle, "what can I say? Earth life is but one of many!"
After giggling a little longer, Peridot suddenly jolts upright, flailing her arms. "OH OH OH I ALMOST FORGOT! You'd probably really appreciate this." Taking the controls, Peridot scans the seafloor for a very particular organic, and after a few minutes she finds it.
"Ta da!" She gestures comically out the window, to which you creep up and give a good look outside. All you see is a small worm-like animal with a notable fin along its entire body and a head tipped with antennae and feelers. You're not particularly impressed. Noticing this, Peridot does a double take. "Are you serious? This is not the reaction I was expecting! You should be gasping in shock!" You give her a deadpan look. "Ugh. I guess I do have to explain everything… Okay. That little animal is called Pikaia. What makes it special is that it was one of the first chordates, the group that includes vertebrate life. You know… fish and reptiles and mammals… including humans like you?"
You nod your head, giving a small "ah" with your voice as you understand. Rolling her eyes, Peridot crosses her arms. "Wow, thanks. Anyway… chordates became unique among animal life in that they developed a stiffened rod along the inside of their bodies called a notochord, which protects the nerve cord. This rod is made of cartilage, which is a hard substance that makes up many parts of your body, like your nose and ears. This was another byproduct of the hardening of animal bodies during the Cambrian. Over time, this notochord was toughened by an extra layer of true bone called vertebrae. That's why you're a vertebrate."
Peridot begins setting the timer. "The Cambrian Period would not be the only time in your planet's history when life diversified into new forms. There were always changes taking place on Earth that set up new obstacles, and organic life either adapted and survived or perished into extinction."
…
460 Million Years Ago
Still surrounded by the ocean, the time machine now resided above a must vaster expanse of seafloor. The small bed of unique organisms has been almost completely changed as great reefs of corals sway and grow in the gentle waters. There are forests of sea lilies (strange relatives of the starfish that look like underwater palm trees) and a variety of snails and clams in-between the corals. There are still plenty of trilobites around too. In the open ocean above you can see jellyfish and other creatures swimming and floating about. In all, it's a much different scene.
"We've now jumped to another period in Earth's history, the Ordovician. A world of tropical oceans, this time saw the rise of brand new ecological niches… those are the roles that organics fill in their environment, be that predator, prey, scavenger, you name it! Animals began to swim further and further out to sea, away from the seafloor, while others started digging deeper and deeper burrows. In essence, the Ordovician set up the marine ecosystem that was to remain nearly unchanged for the next 233 million years!"
Peridot begins to steer the time machine upwards, but accidentally bumps into a giant orthocone (a giant type of cephalopod, with a long vertical shell, that hangs suspended in the water like an icicle). "Whoops! Excuse me!" Peridot shouts, before driving on.
"While the oceans remained crowded with life, it took a little longer for anything to gain a significant foothold on land." Peridot explains as the time machine surfaces, gradually moving along until it reaches the coastline. "Until the ozone layer were properly established, nothing could really live on land at all! And until 460 million years ago, it was almost as barren as it was 3.8 billion years ago. Talk about boring."
The pod rests on a sandy beach, the legs extended out as support hooks. Handing you the breathing mask, Peridot leads you outside once again. The beach, as you expected from her explanation, wasn't as empty as it was before. You can clearly make out fields of green, yellow, and brown alongside small rivers going outwards onto the land. You follow Peridot as she guides you to the freshwater stream, taking a seat next to her as she continues.
"Plants, like all other organics, evolved in the oceans, but the first land plants developed from species that moved into freshwater. These plants were able to support themselves on dry land because they either had flattened leaves (like liverworts) or because they used root-like structures to secure themselves to the ground (like mosses)." After Peridot's explanation, some of the mosses begin sending out very small clumps from their leaves which float in the wind. You back up slightly to prevent them from getting on you. "Hehe, don't get too close! Early land plants, like mosses in the present day, reproduced with spores. These are tiny microscopic cells that float in the wind and, when they land, grow into copies of their parents. But spores only work in wet places, so the first land plants were confined to the moist places by the rivers and streams."
Looking around and breathing in, Peridot sighs contently. "Even with all this green, the land is still pretty much barren. There isn't enough food for animals yet, but the first land plants wouldn't be alone for long. You notice how the ground where the plants are growing is really rich with dirt? That's the first soil, created by the first fungi to join plants on land! When I first started really learning about Earth, I thought that fungi, like mushrooms, were plants, but Steven's friend Connie explained that fungi belonged to their own group of life. They're decomposers, relying on dead organic matter for food. As the early plants began to die, they left behind a buffet of food, and so fungi began to colonize the land too. When they feasted on the plants, their bodies churned the ground, and created soil. And, if you're like me and you love gardening, you know that soil is a big plus for providing plant nutrients. Here, come inside the time machine and I'll show you!"
Back inside, Peridot clicked the special fast-forward dial. This was the first time she used while on the planet Earth, and the view was absolutely spectacular. Day turned to night and back within milliseconds as the landscape changed before your eyes. Mountains rose and fell, canyons widened and shrunk, and gradually the small mossy patches gave way to much denser patches of foliage. Peridot stops fast-forwarding, and opens the time machine again.
"We're now 420 million years ago, hitting another milestone in land plant evolution." Peridot runs out and plucks one of the plants and hands it to you. It's a strange thing between your fingers: a two-inch long branching patch of leafless, woodless stalks tipped at the ends by rounded points. "That tiny plant is called Cooksonia, and it's one of the first plants with vascular tissue. These tissues functioned as a series of strengthened, interconnected tubes that acted like the veins in your body, here providing a delivery system for water to reach every corner of the plant. This was a very efficient system, and that, coupled with the first true roots, allowed plants like these to move much further out into the land."
You feel something crawling on your foot, and you quickly flinch your foot in alarm, sending whatever it was into the foliage. "Hey! Careful!" Peridot shouts, before running towards the plants and picking up the launched animal. "It was only a millipede." she comments, letting the multi-legged animal crawl along her fingers. "Now that there was plenty of food and shelter thanks to the plants, animals were now able to make the first steps onto land. It was arthropods like these that did it first. The hard shells that they developed during the Cambrian proved very good for landlife, their stiff, articulated legs providing support for their bodies."
Gently, she let the millipede back into the small forest. "Once plant-eating arthropods started living on land, it wasn't long before meat-eating ones followed them. Okay… you're actually gonna want to take a step back."
Peridot walks beside you and carefully moves you backward as a couple of scorpions begin marching along where you stood. "Well, would you look at that, we now have fully functioning ecosystems in the sea and on the land! And it only took, what, 3.3 billion years? HA! Homeworld had already conquered all the arms of its galaxy by then."
"Here," Peridot begins leading you back inside, "let's fast-forward one more time and see how the forest changes. You're gonna love this!"
Sure enough, as the dial is switched, the Earth transforms dynamically. But your view of the distant mountains becomes quickly obscured as great trees begin sprouting up all around, until before long the time machine is surrounded by plants, bordered on one side by a shallow lake.
Opening the hatch, Peridot jumps out and cackles into the air. "HAHA! I'm amazing." She turns to you, hopping in place, "isn't this cool?! 380 million years ago and the world finally has trees! And ferns! Plants with actual leaves! Ahh, Lapis would have loved this."
Peridot walks around admiring everything, and you can't help but join her. It is certainly much more appealing than those moss patches, pioneering as they were. "Some of the smaller trees you see here have developed a special mutation that has completely changed their reproductive habits. Seeds." Peridot pulls on the branch of one of these plants and brings it closer to your view. "Unlike spores, seeds are encased in hard shells with food storage for the little plant embryo inside. Seeds were made when land plants began dividing their spores into two different structures: the female spores staying attached to the parent plant while the male spores (called pollen) were sent out from the parent plant to fertilize a different plant. Once connected to the female spore, the pollen fused to it and formed an egg that grew into a seed! All that was left was for the seed to fall, be planted to the ground, and a new plant is made! Earth fusion is so unique from Gem fusion, but special all the same!" Peridot smiled.
Leaving that plant for another one, Peridot ran her hand along the trunk, gesturing you to do the same. As you feel the plant, you notice a familiar toughness to your touch. It's wood. "Some vascular land plants began using wood to support their bodies, and this allowed them to grow to immense heights, hence all these trees you see around you. And this allowed them to move even farther into the land!"
Surprisingly, the forest is still very quiet, and you cup your hand to your ears to try to pick up anything at all. Peridot notices this: "ahh, don't bother. There's nothing to make noises yet. Animal life has flourished on land quite a bit, but nothing that's too chatty. But then again, a conversation with a mite, spider, or snail probably wouldn't be too engaging anyway. All the real action is taking place along the waterways! Come on!"
…
To Be Continued!
