It has almost the same intelligence as an average human child.
Literal
Average human child [with-と] almost same intelligence [object-を] has.
平均的な人間の子供 is 'an average human child.' ほとんど同じ is 'almost the same.' 知能を持っている is 'to possess intelligence' — Japanese uses 持つ ('hold') for many mental states (希望を持つ, 興味を持つ) where English would use 'have.' The doubled いるいる at the end is a typo for plain いる.