I had asked the question to myself about 13 years back. And I realized that I am the universe. Then I asked, what is the universe? The universe is nothing but thoughts. What are thoughts? Thoughts are nothing but potentiality (they can be converted into an actual thought by a conscious being).
The universal consciousness collapsed the first potential thought into an actual thought.
Once the actual thought was born, it collapsed other potential thoughts into actual thoughts (into animate and inanimate objects).
And thus the universe was born.
And finally came the homo sapient species – who extrapolated the universe to the big bang.
Please let me know if you find any flaw in my flow of thoughts, and correct it.