Which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?
A) They are seen in "primitive" cells such as yeast.
B) Yeast cells signal each other for mating.
C) Signal transduction molecules found in distantly related organisms are similar.
D) Signals can be sent long distances by cells.
E) Most signals are received by cell surface receptors.
Answer: C