dietary evolution

[Guest guest]

Hello Kim,

Thank you for this message and bit of information which as

always, is calm, composed, informative, insightful and enlightening. Thought

you might be interested to read this article on the diet of Douc Langurs,

which are leaf eating monkeys. There are some of them in the zoo in

Singapore and I am sure American zoos have them. Maybe you could enquire

about the diet these animals in captivity and if they need supplements for

B-12? What implications would that have for a human vegan diet?

With all good wishes to you and yours for 2009.

Kindest regards and warm wishes,

 

http://www.genomenewsnetwork.org/articles/03_02/leaf_eating_monkey.shtml

Leaf-eating monkey shows gene theory in action

 

By Adam Marcus <gnn

 

March 15, 2002

 

 

 

Thousands of human genes were once copies of other genes that have over time

developed mutations and drifted away from the originals, according to the

theory of gene duplication. Genomics has provided circumstantial evidence

for the theory, but scientists have not been able to show how gene

duplication might lead to new functional genes. Now, researchers believe

they have an example involving a species of leaf-eating monkeys, called douc

langur.

 

Red shanked douc langur female with infant (Southeast Asia).

©Primate Conservation Inc. <http://www.primate.org/>

 

Jianzhi Zhang, an evolutionary biologist at the University of Michigan in

Ann Arbor, and colleagues say gene duplication is behind the uniquely

efficient way douc langurs digest their dinner. After a gene for an enzyme

was duplicated millions of years ago, the species developed a second gastric

enzyme that ultimately turbo-charged its ability to draw nutrients from

leaves.

 

" Duplication is believed to be important for generating new genes and

important for adaptation of organisms to the environment, but it has not

been shown clearly how this works, " says Zhang. " This study provides a

clear-cut case that gene duplication provides the opportunity for the

evolution of new genes. " The study appears online in *Nature Genetics*.

 

Duplication typically occurs when chromosomes pair and recombine sloppily in

a process called 'unequal crossing-over.' Initially, the duplicated gene

performs the same function as the original. But subsequent mutations can

give the copy a unique role. If the mutation has a beneficial effect, the

new gene might survive; if not, it might end up as a functionless

'pseudogene.'

 

Douc langurs belong to a subfamily of Asian primates called colobines, which

split from other Old World monkeys about 15 million years ago. Most monkeys

eat fruits or vegetables and even meat, but colobines primarily eat leaves,

which are more difficult to digest. Their digestive system is similar to

that of cows. In the gut of a monkey are bacteria that ferment leaves and

take in the nutrients they release. Then, the animal digests the bacteria to

obtain proteins and other nutrients.

 

All colobines have a key pancreatic enzyme, RNASE1, which helps them digest

bacterial ribonucleic acid (RNA)—a source of nitrogen. About four million

years ago, douc langurs developed an extra copy of the *RNASE1* gene,

according to Zhang's group. The new gene, called *RNASE1B*, mutated, and its

enzyme ultimately made the monkeys more efficient in extracting energy from

leaves.

 

Douc langurs had been eating leaves for millions of years before the new

gene appeared, says Zhang, so it was not the duplication that turned them

into vegetarians. But it appears to have greatly improved their efficiency

in digesting plants. " This gene was not necessary for the process of

fermentation but it helps, " Zhang says.

 

 

 

On 1/1/09, Kim Bartlett <anpeople wrote:

>

> If humans descended from a line of pure " leaf eaters, " we wouldn't

> have such a problem with B-12 deficiency on a vegan diet. B-12 is

> the only nutrient required by humans that cannot be obtained with a

> purely plant-based diet. Unfortunately, B-12 is absolutely necessary

> for health and it is not easily absorbed in tablet form. Even

> carnivorous humans often start running low on B-12 as they get older,

> and there are some theories that some of the neurological impairments

> of old age may actually be related to B-12 deficiency. Without

> adequate B-12, the body does not produce sufficient red blood cells

> and one becomes anemic, but there are other symptoms. Vegan

> theorists claim people can obtain enough B-12 without relying on

> animal products or vitamin supplements if they refrain from washing

> their vegetables so that there is increased dietary dirt, which may

> contain B-12 producing organisms; however, that isn't exactly

> appealing to most folks, especially when E.coli contamination is

> often fatal nowadays. While primates are largely vegetarian, most

> consume bugs and/or eggs, and many species eat meat. It would be

> interesting and useful if someone could study the sources of B-12 in

> natural primate diets. It might provide some clues about the food

> preferences of proto-humans. While there is no arguing that veganism

> is the most ethical diet for humans, because of the B-12 problem, it

> is a stretch to say that the vegan diet is the most " natural " for

> humans.

>

> --

> Kim Bartlett, President of Animal People, Inc.

> Postal mailing address: P.O. Box 960, Clinton WA 98236 U.S.A.

> email <ANPEOPLE <ANPEOPLE%40whidbey.com>> web-site:

> http://www.animalpeoplenews.org/

> We believe that the Golden Rule applies to animals, too.