as far as 表示直到.为止,在此句中：
句子主干：This latter group could have little Neanderthal DNA in them
插入语：,Dr Sankararaman assumed,
原因状语从句：because Neanderthals lived only in Europe and western Asia.(主干)
,as far as can be determined from the fossil record,( 状语)
所以句意是：
据Sankararaman博士推测,后一个群组的基因里面不可能有尼安德特人的基因,因为迄今为止,从所发现的化石记录里可推断尼安德特人只生活在欧洲和西亚.