[AndrewC]

This is a PRO evolution article. Had horses increased in size over time in a linear progression regardless of habitat changes and other environmental stresses, it could have suggested a mechanism other than Natural Selection was at work, but not ID.

No it wouldn't. The successive small changes in a particular direction is the hallmark of Darwinian theory. Habitat changes and evironmental stresses are a given.

[Soliton]

You are factuall incorrect. Natural selection does not propose 'small changes in a particular direction". Environmental stresses creates evolutionary winners and losers. The winners do not "adapt" to a change in environment, they merely survive. The genetic advantage they have for survival existed as a result of variations in the gene pool due to genetic drift. The genetic differences existed before the particular selection event took place. It only became an "advantage", after the event. If a different selection event had occured, the same genetic difference may have been fatal.