sentence: ceramic c. 25,000 bc domestication of animals , c. 15,000 bc bow , sling c. 9th millennium bc microlith c. 9th millennium bc copper c. 8000 bc agriculture and plough c. 8000 bc wheel c. 4000 bc gnomon c. 4000 bc writing system c. 3500 bc bronze c. 3300 bc salt c. 2500 bc chariot c. 2000 bc iron c. 1500 bc sundial c. 800 bc glass ca .