Tag Archive: species

In many ways this is a retrospective. Walking With Dinosaurs came out almost 12 years ago, in 1999. Last century stuff. But it set the stage for all the dino-documentaries that have come out since.

When it came out, realistic computer-generated dinosaurs were certainly a possibility in movies – Jurassic Park preceded and partly inspired Walking With Dinosaurs. But managing this quality of CGI on a television budget, treating the whole thing as a documentary and bringing in paleontologists not only as advisors but at times as collaborators, was new.

I do have some quibbles with the six episodes. First, there are a few places where the narration is just plain wrong. I’m not talking about things that were learned after the film was made or guesses that are presented as fact; I’m talking about things like the statement that carbon monoxide is heavier than air. In fact, it is almost exactly the same density as air. The suffocating, low-lying gas that is produced by volcanic action, and is heavier than air, is carbon dioxide.

Second, there are many things in the DVD that are pure guesswork. Some of these are pretty obvious, like the colors of extinct animals. No real problem there — they had to be some color, after all, and why not pattern them after existing reptiles? In some cases, such as pterosaurs getting around on the ground, even the paleontologists learned something from the animators’ efforts to get the animals to move. But flat statements such as the one that cynodonts paired for life, for instance, seem sheer guesswork.

Finally, this DVD has to be watched with recognition that a great deal has been learned about dinosaurs in the last 12 years. We now know, for instance, that a great many of the predatory dinosaurs had feathers, probably both for insulation and for display. Our ideas about the social life of dinosaurs are also undergoing a transition. The DVD shows Tyrannosaurs as solitary animals, guarding their territories jealously. There is increasing evidence that they may have hunted in packs, with a social life more like wolves.

Do look at the second DVD, the one that has “The making of” sequence. This points out things that are all too often ignored in later dino-documentaries, such as the fact that grass evolved quite recently, and was never present when the non-avian dinosaurs were alive.

This was the first made of the “trilogy of life” series, though it is the middle one in terms of geologic time. This trilogy is still probably the best of the dino-documentaries.

I’ve been taking an OLLI (Osher Life Long Learning institute) class this month, titled Major Evolutionary Transitions. The presenters are two of my favorites: Dr. Sarah Fowell and Dr. Patrick Druckenmiller, who gave a wonderful course on dinosaurs last year. This time we’re skipping the dinosaurs and looking at eight topics, two a week. The first two were the Ediacaran fauna, soft-bodied animals that lived before animals evolved hard parts that are fossilized in conventional ways, and the Cambrian explosion, the first animals with hard parts.

To look at this transition, we have to look at fossils as more than fossilized bone or shells. That kind of fossil does indeed start with the Cambrian, about 542 million years ago. But there are other kinds of fossils.


Chemical fossils are chemicals produced by life processes, and those go back over 3 billion years. Traces resembling microbes can be found in rocks dated to 3.5 billion years of age. Stromatolites — limestone structures similar to those built today by cyanobacteria — date back to 3.5 billion years ago. (Cyanobacteria? Ever had a fish tank? Think blue-green algae, though they’re not really algae.)

By the late Precambrian multi-celled animals were common, but they had no hard body parts. It takes really exceptional conditions to fossilize a jellyfish or a sponge, but rare fossils of these animals can be found. Then, 542 million years ago, there was a rapid increase first is the number of trace fossils—such as burrows or tracks—and then in actual hard parts. What caused this?

Most likely, a change in sensory input. The senses of smell/taste, being chemically based, are probably very old. I have imagined a planet in Homecoming, Mirror, at a very early stage of evolution where the only hard parts are those secreted by the stromatolite-like land corals. At least one of the soft-bodied animals will swim up-gradient to a particular chemical and attempt to ingest the source of the odor. Chances are that some of the Precambrian animals had similar abilities, and enough nervous system to use them.

Light sensing cells might also have been useful, in avoiding excessive light or in seeking light. (Moving up or down in the water column.) But the evolution of lenses and the compound eyes they made possible may well have set off the evolutionary arms race.

Precambrian animals, as far as we know, did not hunt each other. They may well have eaten each other, as anemones do today. But how could they find each other? And what is the use of armor or skeletons if there is nothing trying to eat you and you don’t need to move rapidly?

Then something evolved the first primitive eyes. It probably wasn’t the best-known predator of the Cambrian, the Anomalocaris, though it may well have been one of its ancestors. Once the eyes were there, even in very primitive form, the hunter could find its prey. The prey animals, such as trilobites, had to evolve eyes as well, to see the predators coming, and hard coverings, to make them harder to eat when caught. The prey animals got bigger to avoid being eaten, and the predators got bigger to catch them. The resultant arms race both speeded up the pace of evolution and produced increasingly large hard parts to be fossilized.

It’s worth pointing out that it took a long time for the Anomalocaris to be recognized as a single animal. Initially, the “arms” near the mouth were thought to be a shrimp-like creature, the ring of plates that made up the mouth were seen as a sort of jellyfish, and the body was thought to be a kind of sea cucumber. The animal was not put together until the 1980’s.

The photos are screenshots from an aquarium program, Aquazone Blue Planet which, in addition to conventional aquariums, has several Cambrian animals and backgrounds.

LAND CORALS: Lai’s name for a form of primitive life on Riya.  They are best thought of as photosynthesizing colonial algae that secrete calcium carbonate, living in the wave zone on land. The calcium carbonate towers can be up to a couple of meters in height.

CROSSBREDS: a generic term for individuals who have at least one parent with obvious R’il’nian traits. All R’il’noids are crossbreds, but many crossbreds have Çeren indices well below the 72 required for classification as R’il’noid.


XIRA: The R’il’nian equivalent of mice.

Real planets come in all sizes, geographies, climates, geologies, and probably ecologies. They circle a wide variety of stars. But they do all follow certain physical laws, and these laws constrain how the various aspects of a planet work together. Orbital mechanics and the physics of how stars work do provide some limits. In inventing a planet, you need first to consider what you require of that planet. Is it to be a carefully chosen object for colonization by human beings? The site of an accidental colonization? An uninhabitable world with something worth exploiting? The home of a non-human and totally alien species? A base for scientific exploration?

For Homecoming I invented three planets. Two are intended to be fully livable, Earthlike planets, the results of long-ago modification. Both circle sun-like stars and have climates, year lengths, day lengths and axial inclinations similar to Earth’s. The ecology of Central is assumed to be a mixture of species imported from Earth and the home planet of the R’il’nai, and differences from Earth ecology are unimportant for this story, though they do exist. That of Riya is a combination of a native ecology with that from R’il’n. In the native Riyan ecology, land animals with internal skeletons have six, rather than four, limbs. This allows for four-legged animals with wings, like the little lizard-like animals that act as pollinators for the native vegetation. Photosynthesizers also differ from Earth’s, with a growth structure based on expanding sheets (with holes) rather than branches. Both planets have components—like the tinerals on Riya—brought in from planets other than the primary sources.

On the third planet, Mirror, I let my imagination go. This is not a comfortable planet for human beings, nor is it intended to be. It is, however, modeled on the early stages of evolution on Earth, with an interesting twist—both left-handed and right-handed biochemistry co-exist. Is this possible? I don’t know, and neither do my characters. But every scientist I know would agree that this is a planet to be preserved for study, not colonized. Mirror circles a star much like our sun at a distance that allows water to be liquid, so as real planets go it’s pretty tame. Its atmospheric pressure is high—like that of early Earth—with a significant fraction of the pressure coming from carbon dioxide, which contributes to its hot climate. There is nothing surprising about a planet having lots of water and carbon dioxide. Hydrogen, carbon, oxygen and nitrogen are the four most common reactive elements in the universe, so we expect their compounds to be common. Water is just hydrogen and oxygen, while carbon dioxide is carbon and oxygen. What is unusual is to have free oxygen, as on Earth, and pressure and temperature that allow water to be liquid.

On Mirror the process of combining carbon dioxide and water to produce carbohydrates and free oxygen, using sunlight as an energy source, is just getting started. There is oxygen in the air, but not enough to support much in the way of land dwellers. My castaways are quite reasonable in wanting to get away as soon as possible—they’re not properly equipped for the scientific study they recognize the planet needs. Besides, they want to get home! I’ll have more to say on planet building later. For now, welcome to my blog and I hope you surf on over to my website and find out what Homecoming is all about (www.sueannbowling.com).