What Darwin Didn't Know by Geoffrey Simmons

Author:Geoffrey Simmons [Simmons, Geoffrey]
Language: eng
Format: epub, mobi
Tags: Christian
ISBN: 9780736936729
Google: KP4jFvD_RHcC
Barnesnoble:
Publisher: Harvest House Publishers
Published: 2009-11-20T00:00:00+00:00

Bones, physiology, the nervous system—the body has thousands of consummate designs that elicit our wonder and admiration.

—Randolph Nesse and George Williams, Why We Get Sick

14

The Endocrine System

The endocrine system includes the pituitary, thyroid, and adrenal glands, the testes and ovaries, and numerous smaller islands of tissue located in the pancreas, heart, lungs, brain, kidneys, stomach, liver, and placenta. Each gland produces specific hormones that carry messages to target cells, telling them what to do, when, and how. To date there are more than 40 hormones known, and the production of each one is controlled by a feedback loop. Many work in parallel or tandem, some compete, and some have double and triple feedback loops. The overall complexity, the necessity for the WPP—whole package phenomenon—and the need for all systems to be in place simultaneously strongly challenge evolutionary theory.

The concept of a feedback loop may sound intimidating, but each of us operates with similar models every day. Many large corporations and government agencies make major decisions based on feedback. Picture a person who is responsible for keeping the daily supply of cookies for New York City at a constant number. Not only does he keep track of every cookie consumed on a microsecond-to-microsecond basis, but which types are preferred; he can adjust to every change. No one wants a backlog of stale cookies. If, for example, the supply of macaroons drops precipitously, every baker in town is immediately told to increase production. If the Chinese restaurants cut their orders of fortune cookies, appropriate bakers are told to slow production. If a huge Boy Scout convention comes to town, the bakers might be told to increase manufacture of chocolate-chip. If the convention is then canceled due to bad weather, production is stopped. Actions depend on reactions and vice versa.

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