22.0 Milieu

Catastrophe Species. This game starts in the aftermath of the biggest disaster ever recorded, the Permian extinctions. The rock layers before this incident record wet forested jungles and coals. Afterwards are the sandstones of the Early Triassic, monotonously barren the world over. For a game turn (10 million years) the plant record shows only a few “disaster species”, cosmopolitan weeds such as spiky quillworts, shrubby lycopods, a seed fern, horsetails, and dwarf conifers. The marine fossils are also opportunists: small scallops or brachiopods adapted for low oxygen waters. The first trees and conifer forests appear halfway through the turn, populated by small unspecialized archetypes such as those in the game. Biodiversity and biota were still recovering through game turn two. It is estimated that over 90% of the animals worldwide were a single species of two-tusker.

The Struggle of Dynasties. The Triassic Period, a time of struggles for megafaunal world domination, lasted for 5 game turns. The two-tuskers, the top herbivores, were edged out by the chisel lizards and dog-faces. The top carnivores were also dog-faces. But at the end of the Triassic, Pangea split along the Atlantic Rift, erupting huge flood basalts³⁴ and skyrocketing the Greenhouse. In the resulting mass extinction, dog-faces, chisel lizards, and two-tuskers died out, and a previously obscure group gained the field, the dinosaurs.

American Megafauna. The north-south orientation of the two American mountain ranges act as a “climatic trumpet”, magnifying the effects of Greenhouse levels. America’s ice-sheets were the most extensive in the world, and its Eocene tropics were the balmiest in the world. The collision of funneled arctic blasts with tropical air spawns most of the world’s tornados. These extremes have forged America into a kind of megafaunal evolutionary superpower. It has spawned the biggest and the most dinosaurs, and appears to be the origins for the ruminants (cud-chewers such as cows, sheep, deer), camels, and perissodactyls (horse, rhinos, tapirs). (However, few if any bird orders originated in America for some reason.) Mammal diversity peaked 15 million years ago in the Miocene, with American savannas resembling the Serengeti. America lost its megafauna during the Pleistocene ice ages, likely because of human invasions over Beringia.

Vegetable Emperors. During the Cretaceous, an organism developed more fearsome than all the dinosaurs stomping around. The first flower bloomed. Angiosperms use flowers to employ legions of insects to handle their pollination, and use fruits and nuts to employ animals for seed dispersion. At 50 million years ago, and again 38 million years ago, the greenhouse fell dramatically. As usual, the climatic effects were magnified in America. The rainforests opened up as things got drier. As seasonality increased (i.e. greater differences between summer and winter), the first angiosperm weeds developed, annuals that die off every winter to be reborn. And the first wind-pollinated grasses bloomed, the most successful and advanced of the angiosperms, which actually tamed fire before the animals did. The increased seasonality also gave angiosperm deciduous trees the edge over conifers. By dropping leaves in the winter, a deciduous tree can handle winter drought better. And it can recoup much of the nutrients expended to make the lost leaf when the leaf rots the next spring. In regions where tropical summers follow arctic winters, deciduous trees have the edge. Where the summers are not quite so balmy, evergreens have the advantage. And where the winters are not quite so frigid, angiosperm evergreen broadleafs have the advantage.

Dinosaur Mysteries

Perhaps while playing this game, you can figure out the three fundamental dinosaur mysteries:

1. Dinosaurs are big. Reptiles, birds, and mammals developed tiny species, but never dinosaurs.

2. Dinosaurs are terrestrial. Reptiles, birds, and mammals have had marine and flying forms. Not dinosaurs.

3. Dinosaurs are dead. Reptiles, birds, and mammals all had survivors. Dinosaurs didn't.

Size Matters. This is a game about megafauna, animals 100 kg (220 lb) or more. In the history of life, animals this size were rare until the Mesozoic Era began a quarter billion years ago. Why be big? Megafauna gain a disproportionate share of the resources in an area. Large animals are often faster, migrate further, and can catch bigger prey than small ones. Weight per weight, megafauna need less food than small animals and do not need a high metabolism for the same activity level. Finally, large animals have smaller populations than small ones, given a constant resource. Smaller populations exhibit more speciation, at the price of greater genetic drift.

Warm-blood vs. Cold-blood. Large creatures can maintain their temperature at metabolic optimums easier than small ones. One can visualize this principle by observing how fast a given amount of ice melts in cubes compared to if it is in one big block. Creatures with a relatively constant body temperature are called homoiotherms. Some megafauna, such as crocodiles and big turtles, are low metabolism homoiotherms and maintain their body temperature through thermal mass. Other animals, with higher metabolisms, must expend energy to maintain a higher body temperature. A 50 kg cougar eats five times that of a 50 kg alligator. A body temperature of ~38°C is optimal for chemical reactions (including digestion and Krebs cycles) and muscle performance. Tiny homoiotherms like shrews and hummingbirds must eat continuously to maintain this temperature.

Foregut vs. Hindgut Digesters. Most of the energy of a leaf is locked up in cellulose, the most common component of fiber. No known animal can digest cellulose without lengthy digestive tracts filled with special bacteria. These tracts include the foregut (stomach or crop) or hindgut (colon or intestine). The hindgut fermentation digesters include elephants, rhinos, hippos, horses, and extinct sloths, ankylosaurs, and pachycephalosaurs. A large amount of foliage can be processed rapidly in the hindgut, but the droppings will contain much undigested food. Elephants spend 77% of their time eating because of digestive inefficiency. Foregut digesters, such as ruminants, are more efficient because the vegetation in the crop can be regurgitated forward for additional processing and mastication. Deer, giraffe, camels, goats, bison, and cattle are today’s foregut digesters.