How Old are humans?

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Across
  1. 2. simple past of build
  2. 5. same as houses use for be safe
  3. 8. savage animal, is like a dog
  4. 10. same as years
  5. 12. comparative of smart
  6. 14. past simple of help
  7. 15. opposite of old
Down
  1. 1. you wear them (pans, skirt; etc)
  2. 3. opposite of short
  3. 4. survived present perfect of survive
  4. 6. axes, spears; etc
  5. 7. past simple of make
  6. 9. same as big
  7. 11. made of bones
  8. 13. comparative of tall