### Challenge Problem 1: Phylogenetically Independent Contrasts

Download the following two files:

- pic-exercise-data.csv
- pic-exercise-tree.tre

Fit a OLS (non-phylogenetic) regression model for `y~x`

and a phylogenetic
regression model using contrasts. What do you find? Why?

*Written by Liam J. Revell. Last updated 11 December 2017*