There was a market for whether "love is the most important thing in the universe". Let me make an improved version with a more plausible claim. I want to see how it fares comparatively.
Within "reproduction", I include many things related to reproduction by natural selection, such as sexual and asexual reproduction, sex, hormones, carnal pleasure, romance, love, and other things that might be directly related to reproduction by natural selection.
Interpret "important" however you prefer. The ambiguity makes it kinda interesting.
I exclude the necessary physics for biological entities to exist in the first place as an alternative answer to the question. I simply take them as a given. By this, I mean that the existence of dimensions, space, time, atoms, gravity, the nuclear forces, electromagnetism, planets, heat, and other preconditions for life are presupposed and thus disqualified from the competition as "more important".
Conditions for resolution: I will let the market stabilize for three months, and then if it reaches >80% I will resolve YES, and if it reaches <20% I will resolve NO. Otherwise it will stay open indefinitely. I could resolve N/A if I see blatant market manipulation (including cases such as the market being decided by a single person betting a ton on money on one side).
Related questions
Reproduction is a fundamental feature of all known life, and it is a biological process through which living organisms produce offspring similar to them, here are some reasons why reproduction is important for biological beings:
Reproduction helps in maintaining balance between birth and death rate.
Reproduction brings variation which further leads to evolution.
Reproduction helps in the continuation of species.
that why I strongly believe reproduction is the one and only way to maintain a perfect ecosystem and sex produce serotonin and endorphins that helps the body to with mood stabilizer and pain reliever.
@KashalaOrnella thanks for your comment but I think it requires more data. For start, I believe that assume that reproduction is the most important thing in the universe for biological beings is a generalization. In terms of human beings, there is important data that supports the fact of the importance of reproduction.
Fertility is one of the most important factors in terms of demographics since population age has economic and social implications. https://www.britannica.com/science/population-biology-and-anthropology/The-developing-countries-since-1950 and https://globalnews.ca/news/9836414/canada-immigration-aging-report/#
Global fertility as decreased from 2.3% per year to no even 1% today. https://ourworldindata.org/fertility-rate
The following images show how fertility has decreased throughout the years.
Humans are sexual beings, marriage is the first institution for humans after creation and union is far more to be desired than anything else. Most motivational theories give mention to the importance of social connection to be important to the livelihood of human beings. Maslow even put sex as a physiological need, thus a need for existence. Regardless of one’s sexual orientation, humans have someone or some people who they endings with. Imagine a world with men alone, we would not have a motive to work. Based on the above facts, I say YES.