Migrants have Facebook and WhatsApp on their phones, and they can report what happens to them along the way. They span networks by nationality, like the one Malians and Senegalese have been building in Brazil and Argentina since the late 1990s. In chat groups, those who have already made it through put them in contact with some migrant protectors — like Luis Guerrero Araya, whom I met in La Cruz, Costa Rica — and they can let others know if there are problems ahead.
Once some find soil to put down roots, they call the others, and those call others. This is what humanity has always done: migrate in clusters.
This long journey is also possible because, although migrants are unwelcome almost everywhere, their money is always welcomed. It flows easily from accounts in Karachi, Pakistan and Douala, Cameroon to Cruzeiro Oeste and Sao Paulo, Brasil or to Apartadó, Colombia, it crosses all borders with very little paperwork, through multiple international instant money transfer services like Western Union or MoneyGram, which are often mentioned.