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Encyclopedia > Allen's Rule

Allen's rule is a biological rule posited by Joel Asaph Allen in 1877. It states that endotherms from colder climates usually have shorter limbs than the equivalent animals from warmer climates. Biology (from Greek βίος λόγος, see below) is the branch of science dealing with the study of life. ... Joel Asaph Allen (July 19, 1838 - August 29, 1921) was an American zoologist and ornithologist. ... A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down...



The theory behind Allen's Rule is that endothermic animals with the same volume may have differing surface areas, which will aid or impede their temperature regulation.

Consider eight boxes of equal volume, 4 units to a side. If you create a stack two boxes wide, one long and four tall, you will have a volume of 64 units with a surface area of 112 units. If you create a stack of boxes in a cube shape two boxes wide, two long and two high, you will have the same volume of 64 units but a surface area of only 96 units.

In cold climates, the greater the exposed surface area, the greater the loss of heat and therefore energy. Animals (including humans) in cold climates need to conserve as much energy as possible. A low surface area to volume ratio helps to conserve heat.

In warm climates, the opposite is true. An animal will overheat quickly if it has a low surface area to volume ratio. Therefore, animals in warm climates will have high surface area to volume ratios so as to help them lose heat.

The Inuit and the Masai

In anthropology the contrast between the Masai and the Inuit people is often presented as an example of Allen's rule.

The Inuit people live and hunt within the Arctic Circle. The sub-zero temperatures encountered in the arctic environment mean that heat conservation is essential. A short, squat body shape will help retain body heat. For other uses, see Inuit (disambiguation). ...

The Masai people live primarily in Kenya and North Tanzania. The equatorial temperatures in this environment mean that heat loss is highly beneficial. A tall, long, body shape will help get rid of body heat. Masai can refer to Maasai, also known as Masai, the name of an African ethnic group from Kenya and Tanzania Masai, Johor, a suburb of Johor Bahru city This is a disambiguation page: a list of articles associated with the same title. ...


It is important to remember that exposure of exterior surface area is only one of many mechanisms by which humans retain or dispose of body heat. The following mechanisms are also very important:

Sweating (also called perspiration or sometimes transpiration) is the loss of a watery fluid, consisting mainly of sodium chloride (commonly known as salt) and urea in solution, that is secreted by the sweat glands in the skin of mammals. ... Shivering is a human bodily function in response to cold. ... Historical data for native populations collected by R. Biasutti prior to 1940. ... Behavior or behaviour refers to the actions or reactions of an object or organism, usually in relation to the environment. ...

See also

Polar Bear In zoology, Bergmanns Rule is a principle that correlates environmental temperature with body mass in warm-blooded animals. ... Glogers Rule is a zoological rule which states that within the same species of endotherms, more heavily pigmented forms tend to be found near the equator and lighter forms away from the equator. ...


Joel Asaph Allen. "The influence of Physical conditions in the genesis of species." Radical Review, 1877, 1: 108-140.

  Results from FactBites:
No. 01-3404 (708 words)
The Allens made complaints to Maki concerning the condition of the premises, the timeliness of repairs and access to the basement for storage and laundry hook-up.
The Allens assert that Maki's decision to terminate their lease was a retaliatory eviction and that the trial court erred by finding otherwise.
The effect of the Allens' interpretation is that a landlord may not choose not to renew a lease at the end of a lease term whenever a tenant makes a complaint to a housing code authority.
Legal Database (441 words)
Negotiations between the Allens and the Vendors led to the execution of a purchase agreement.
Allen testified he did not consider Rush to be his agent, and Rush testified that he was acting solely for the Vendors.
An administrative rule governing conduct of real estate agents and brokers, requiring prompt tender to the Vendor of every offer to purchase, does not create a private cause of action in favor of the prospective purchaser against an agent of the Vendor for whom the agent was acting as the exclusive broker.
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