history - A natural explanation for the significance of the numbers 7 and 40

In the Jewish religious texts the numbers 7 and 40 seem to appear quite often and carry special significance. Some examples among many:

• God's creation lasts 7 days


• The Great Flood was from rain falling for 40 days and 40 nights


• Noah brings 7 pairs of every kind of animal he can find


• Moses wrote the Ten Commandments over the course of 40 days and 40 nights


• Debts are cancelled every 7 years

And so on and so on.

I am curious as to natural explanations as to why these two numbers came to hold such significance. I'm not interested in how these numbers are represented as holy numbers in Jewish texts, but rather thoughts, theories, or (ideally) knowledge on why people living thousands of years ago came to attach such significance to these two numbers.

My presumption is that the number 7 has long been regarded as special by many cultures due to the fact that there are 7 heavenly bodies visible to the naked eye: the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. For instance, the names of the days of the week correspond to these seven heavenly bodies.

But I am uncertain as to where or how or why the number 40 would have gained such significance.