On Alien Design

The Reasonable Alien: Excerpts from early drafts of my recent SFSignal post.

  • Further thoughts on a possible analytical model for the design of “evolving” sentient aliens.

In broad terms, one would proceed by:

1) Selecting a general earthly animal type or species to use as a basis for the alien species to be evolved, and the geologic age of Earth (epoch) at which that species began the major part of its evolutionary journey.

2) Noting

a) key stable features of planet Earth – its mass and gravitation (also atmosphere
after oxygenation)
b)cataloging, beginning, with the geologic age (epoch) identified in 1) above

i) the Earth’s major changes in general Tectonism/topography and climate
ii)the epoch of each major change
iii)the time intervals between each epoch and the next,
iv)the dominant evolutionary changes observed in the selected Earthly life
form during each interval, in response to those planetary changes.

3) Noting key stable features of the alien world (perhaps a near-Earthlike exoplanet, or another exoplanet more nearly like that proposed for the story,) setting evolutionary epochs for it parallel to those used for Earth.

4) At each epoch, adapting and cataloging for the alien planet its own generalized topographical and climate changes, based on those of Earth and modified based on differences between the alien planet’s key stable features and Earth’s.

5) At each epoch, adapting the Earth species’ dominant evolutionary changes to those of the alien planet, based on the intensities of the topographical and climate changes estimated for the alien planet as compared to Earth’s.

6) At each epoch, applying the alien planet’s adapted evolutionary changes to the animal form selected above as the basis for the alien form.

7) Adding such intellectual, psychological, and/or sociological features, as well as dexterity, sensory, and other capabilities, as needed for the proposed alien and not in conflict with major “evolved” characteristics of the alien. Any such conflicts that do arise should be resolved logically according to the alien and planet designs.


  • Further environmental and sociological conditions that could affect the evolution of sentient aliens.

There have been significant discoveries in cosmology, astronomy, and especially planetology, with its fabulous, ever-growing gallery of exoplanets. Biology and the environmental sciences describe key features a planet would need to evolve and sustain lifeforms. Is its gravity strong enough to retain a breathable atmosphere? Is it rich in carbon, hydrogen, oxygen, and nitrogen, the basics of nutrition as we know it, or in other elements supporting life in other forms? Is it near enough to its star that surface ices melt into free-flowing liquids, to dissolve and circulate the nutrients through the ecosystem? Is it cool enough for the creatures to survive?

But no planet is free from challenges. Eccentric orbits and axial tilts may cause wild swings in day/night intervals, or extreme seasonal variations, or no seasons at all. There will be violent storms, earthquakes, volcanoes and, most certainly, sharp-toothed carnivores of land and sea. Should our sentient hibernate? Should it have claws? Should it run? Or swim? Or fly? How fast and how far? Such decisions, along with gravity and atmospheric density, will shape its form and determine the function and strength of its muscle and bone. Is that enticing plant edible, or a ticket to sudden death? The function and keenness of its mind and senses will adapt to help identify the dangers.

Eventually, societies and cultures will also find ways, whether fair or foul, to address the planet’s challenges. The results of those actions will shape the world’s history. Psychology and sociology give important insights into the ways we are shaped by our educational environments, the our history, and our cultures.


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