DNA home test variances

Many who have done a DNA home test begin to question their family heritage and wonder if they might have been misled. However, taking DNA tests from different companies reveal wildly varying results. There are a few reasons for this: 

• The companies are only looking at very recent DNA samples, from a relatively small group, in one specific database.
• The databases are skewed towards different parts of the world. Some have more American customers and other more British or Australian customers.
  
• These companies don't ask about the genetics of the past, and which of those past inferred genetic clusters we get our ancestry from.
  
• We probably inherit very few genes from our ancestors. DNA is inherited in “chunks” that break up the further back in time you go.
• There are ancestors from whom you inherit no DNA.