The fact does remain that modern society is guilty of injustice, violence and disobedience described in Noah's time. We don't really need Jashar to prove that God prohibited the mixing of diverse species of animals, which is going on today with GMO and hybrid interspecies mixtures. We also do not need Jashar to observe the mischief of fornication and adultery encouraged by the widespread availability of birth control. Even though Justice Goldburg's US Supreme Court Decision in the 60s claimed Planned Parenthood would only provide birth control to married couples and it was a matter of marital privacy protected by the 9th Amendment, someone ought to compare the bored housewives of today and 50% divorce rate with our grandmothers and see if the rate of adultery or STD-increase is dubious, as the judge referred to Connecticut's claims.
There is more sin out there, more guilt which means more evil in the world as in the prediluvian times. It's just begun and can be stamped out by the human race's repentance and refusal to sin. People need to quit believing the serpent and follow their Creator.
The one that we have is an 18th century work of fiction.
Also, to be fair -- about hybrid interspecies mixtures -- there have been mules for millenia.