MIAMI — For the past year and a half, with scant public attention, squads of archaeologists digging at the Miami River site of a planned Related Group residential tower complex have unearthed remarkable finds, consisting of thousands of fragmentary prehistoric tools and artifacts, rare and well-preserved animal and plant remnants, vestiges of ancient structures and human remains — including some relics dating back to the earliest days of civilization on the planet. Independent scientists say the findings, which include 7,000-year-old spearheads, are clear and abundant evidence of a continuous ...