Genuine question, how much evidence of agriculture would survive an ice age, being crushed under the weight of 2 mile thick ice sheets and then washed away or engulfed by bodies of water once they've melted?
Major regions in which early humans evolved and migrated have not been subject to glaciation since those events. Africa, Mesopotamia, Egypt (part of Africa), the Mediterranian basin, the Indian subcontinent, most of China and Southeast Asia, central and Southern America, and much of North America, particularly south of, say, the modern Mason-Dixon line.
The regions heavily affected by glaciation are relatively few, relatively lately settled (for obvious reasons), and hence, less significant to overall availability of evidence of early agriculture.
Other disturbances resulting from glaciation, notably sea level rise and the innundation of previous coastal and low-lying regions may contribute somewhat more to obscured evidence.
