Digirtu waxay ka mid tahay geedaha ugu taariikhda dheer ee dadku beeran jireen tan iyo ilbaxnimooyinka ka hor, wakhti hada laga joogo 10,000 sano. Sida caadiga ah digirta waxaa maanta laga beerta meel kasta oo caalamka ah, marka laga reebo Antaraktika. Wadanada Baraasiil iyo Hindiya aya ugu badan soo saarida iyo beerida digirta qalalan, halka wadanka Shiinaha ugu badan yahay nooca digirta cagaaran. Sanadkii 2010ka waxaa caalamku guud ahaan soo saaray 23 milyan oo digirta guud ah iyo 17.1 milyan oo digirta cagaaran ah.