The Maya were noted as well for elaborate and highly decorated ceremonial architecture, including temple-pyramids, palaces and observatories, all built without metal tools.
For example, early models of high-speed railroad cars loaded with sophisticated controls were unable to operate in a snowstorm because a fan sucked snow into the electrical system.
Lash's biography revealed a complicated woman who sought through political activity both to flee inner misery and to promote causes in which she passionately believed.
After the fall of Rome, the first European society to regulate behaviour in private life in accordance with a complicated code of etiquette was twelfth-century Provence, in France.
You can argue that learning another language well is more taxing than, say, learning to play chess well—it involves sensitivity to a set of complicated rules, and also to context.
Support for this idea came from the observation that long-lasting climax communities usually have more complex food webs and more species diversity than pioneer communities.
Because complex species interactions may be involved, identifying a keystone species by removing the species and observing changes in the ecosystem is problematic.