In the ancient days of Yore, when megabytes were something you got from a big dog and touring bikes were used for touring, Merino wool was the king in hot or cold weather. All of the synthetics claim to wick moisture and sweat away, wool actualy does it. the wool suspends the moisture and as the air follows through the fabric to your body it creates a cooling effect
Wools demise as a fabric for cycling was not that the synthetic fabrics are better. Synthetics are cheaper to produce and are easier to print graphics on. Every few years a company comes along trying to market wool as a great discovery.