Parsimony

n. miserliness, stinginess; extreme frugality or thriftiness

Parsimony is a 'less is better' concept of frugality/economy/stinginess or caution in arriving at a hypothesis or course of action. The word derives from Middle English parcimony, from Latin parsimonia, from parsus, past participle of parcere: to spare.
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Noun
1. extreme care in spending money; reluctance to spend money unnecessarily
(synonym) parsimoniousness, thrift, penny-pinching
(hypernym) frugality, frugalness
2. extreme stinginess
(synonym) meanness, minginess, niggardliness, niggardness, parsimoniousness, tightness, tightfistedness, closeness
(hypernym) stinginess
(hyponym) pettiness

(n.)
Closeness or sparingness in the expenditure of money; -- generally in a bad sense; excessive frugality; niggardliness.
  

The scientific convention whereby the simplest explanation is preferred over the others. This is usually a phylogenetic tree requiring the fewest evolutionary steps.