Orb webs, like the work of the Araneoid spider (Argiope trifasciata) shown above, may have originated as far back as the Jurassic period. Recent genetic and fossil evidence points to a single orb weaver ancestor that probably lived at least 136 million years ago. Two modern day groups of spiders, the Deinopoids and Araneoids, build orb webs. Most arachnologists believe the two groups probably had a common ancestor, but because Deinopoid silk is dry and Araneoid silk is coated in a sticky glue, there has been some debate. A paper in the current issue of Science confirms that the two spider groups share key silk genes--evidence of a common ancestor. A separate paper in the same issue describes fossilized web fragments from the Jurassic period, encased in amber, which could be the work of such an ancestor.