<story><title>Cave discoveries suggest humans reached Americas much earlier than thought</title><url>https://www.nature.com/articles/d41586-020-02190-y</url></story><parent_chain><item><author>mehrdadn</author><text>Question: how do experts tell something like this might be a tool? As a layman it looks like a rock to me:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;media.nature.com&amp;#x2F;lw800&amp;#x2F;magazine-assets&amp;#x2F;d41586-020-02190-y&amp;#x2F;d41586-020-02190-y_18201476.jpg&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;media.nature.com&amp;#x2F;lw800&amp;#x2F;magazine-assets&amp;#x2F;d41586-020-02...&lt;/a&gt;</text></item></parent_chain><comment><author>oxfordmale</author><text>These kind of tools have multiple fracture all running in the same  direction. This means they are not a by product of accidentally tumbling against other rocks. Something has banged that rock over and over in the same position.</text></comment>
<story><title>Cave discoveries suggest humans reached Americas much earlier than thought</title><url>https://www.nature.com/articles/d41586-020-02190-y</url></story><parent_chain><item><author>mehrdadn</author><text>Question: how do experts tell something like this might be a tool? As a layman it looks like a rock to me:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;media.nature.com&amp;#x2F;lw800&amp;#x2F;magazine-assets&amp;#x2F;d41586-020-02190-y&amp;#x2F;d41586-020-02190-y_18201476.jpg&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;media.nature.com&amp;#x2F;lw800&amp;#x2F;magazine-assets&amp;#x2F;d41586-020-02...&lt;/a&gt;</text></item></parent_chain><comment><author>DanBC</author><text>I think they look for &amp;quot;Conchoidal fractures&amp;quot;, and then where they find the thing.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.sandatlas.org&amp;#x2F;conchoidal-fracture&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.sandatlas.org&amp;#x2F;conchoidal-fracture&amp;#x2F;&lt;/a&gt;</text></comment>