What did the greeks think fall was caused by?

The greeks thought that the season fall was caused by the deal Zeus struck with Hades regarding Persephone and Demeter.

Explanation:

Demeter is a goddess that lives on Mount Olypus. She is the goddess of the harvest and would often come down from Mount Olympus to check on her crops. Demeter also loved her daughter Persephone and could not bear to be away from her for long so, she would bring Persephone with her.

Persephone was especially known for her beauty and was also described to be a particularly happy and carefree child. One legend states that wherever she walked, flowers would grow in her path. She could often be found picking bundles of the very flowers she caused to grow in order to present it to her mother, Demeter, as a gift. She was always portrayed as happy and in harmony with every living creature.

On one of the trips that Persephone took with her mother, Hades caught a glimpse of the beautiful girl as she was in a field picking flowers. Hades was the brother of Zeus and Poseidon and the ruler of the underworld, and he was constantly surrounded by images of death. The fact that Persephone was not only beautiful, but also full of life, was especially appealing to him.  Not only that, but he was incredibly lonely. He wanted to make Persephone his queen.

When hades saw Persephone picking flowers in the field, Demeter was nowhere to be found. Persephone had strayed from her mother’s side in order to pick a particularly beautiful flower for her. Hades used this opportunity to grab her and take her down to the underworld. She became his queen by force, and Demeter had no idea what happened. She just knew that her daughter was gone. In her grief and depression, all the crops died and the harvest was ruined.

Because the relationship between Hades and Zeus is a complicated one, Zeus didn’t initially want to get involved with the conflict. However, Demeter’s depression was affecting every living thing and according to some sources, led to a famine that lasted a full year. At first, Zeus tried talking to Demeter about the problem, but she said that she wouldn’t end the famine until her daughter came back to her.

Zeus had no choice – he struck a deal with Hades that would allow Persephone to be by her mother’s side for six months out of the year. Thus, the four seasons were born. During spring and summer, Persephone was by Demeter’s side and the harvest was allowed to thrive. In fall and winter, Persephone was with Hades, which would cause Demeter to become depressed.

an era of negotiation.

is that an answer to your question?

answer:   migrations were important in the neolithic period. "two major migrations passing through southeastern europe were confirmed by the means of archaeo-genetic studies."

the first migration was the early neolithic period -- 6,000 before common era (bce) -- when the first farmers, from anatolia -- asia minor -- spread through europe. the second migration occurred during the early bronze age (3,000-2,500 bce) when the so-called "steppe population," from the eurasian steppe, replaced much of northern europe's previous population.

the first farmers of northern and western europe passed through southeastern europe with limited hunter-gatherer genetic admixture, which occurs when two or more previously isolated populations begin interbreeding. however, some groups that remained mixed extensively -- without the male-biased, hunter-gatherer admixture that prevailed later in the north and west, according to latest discoveries. southeastern europe continued to be a nexus between east and west, with intermittent genetic contact with the steppe people up to 2,000 years before the migrations that replaced much of northern europe's population.

"in some places, hunter-gatherers and incoming farmers seem to have mixed very quickly," says iain mathieson, a geneticist at the university of pennsylvania, who was first author of the paper. "but, mostly, the two groups remained isolated, at least for the first few hundred years. these hunter-gatherers had been living there for thousands of years, and it must have been quite a shock to have these new people show up -- with a completely different lifestyle and appearance."