Too many cooks spoil the broth

Proverbial Meaning: It's often better for just one person, or a very small group of people, to undertake a complicated task. 

Literal Origins: When making broth, or soup, the recipe can be spoiled if there is more than one cook adding their preferred ingredients. 

Common Usage: This proverb is very well-known and quoted as a warning against spoiling the outcome of a one-person concentrated effort by employing extra people for the task.

Adversely see also: Many hands make light work .