Carbohydrates
Carbohydrates are a type of nutrient are found in many foods including: fruits, vegetables, cereals, grains and sweets. Carbohydrates serve as a fuel, providing us with energy and playing a role in brain and organ functioning. Carbohydrates also provide fiber, that is important for excretory functions. There are many types of carbohydrates that have different effects on the body, such as: simple carbohydrates, complex carbohydrates, sucrose, fructose, lactose, etc. 
        
             
        
        
        
Explanation:
First do the Last, First, Then middle names of the author(s). Then the title of the article, then magazine. after that the date it was published and finally the page number the information was found on. example: Last, First Middle "title of article" title of magazine 
 
        
             
        
        
        
ANSWER:
Its because mother nature tells us herself!
its just like predicting when rhinos will go instinct:
imagine people killing 2 rhinos a week or every two weeks and theres only 500-1000, you can predict that in prob 3-5 years they'll go instinct 
so its just like that and they have much higher technology now that it'll just give them the answer without putting much effort into it.
~batmans wife dun dun dun....