Complex sentence: The findings pertaining nomadic peoples of the Asian steppe contradict those theories that maintain that these peoples had strong customs favourable to first or last sons; the only custom that distinguished between sons in these societies was the greater respect that the first son received from his siblings.
Split into simpler sentences: The findings pertaining nomadic peoples of the Asian steppe contradict those theories that maintain that these peoples had strong customs favourable to first or last sons. The only custom that distinguished between sons in these societies was the greater respect that the first son received from his siblings.