Papua New Guinea (PNG) is strikingly similar to East Africa (i.e. Kenya, Tanzania, Uganda and Rwanda, that we visited in July and August 2009). It remained unclear why these two regions that are geographically so remote from each other are otherwise so similar. The following just lists the similarities and also a few differences.
Note that the following is based only on a fraction of PNG — within 10 days we saw a bit of the Highlands (areas around Mount Hagen and Goroka) and a bit of the coast (Madang and around), but didn't go into the large towns (Port Moresby, Lae) and to the islands (e.g. Rabaul).
Nature/climate is similarly tropical as the region lies only a few degrees below the equator. Higher regions (altitudes around 2000m) can get quite cold during the evenings. In these regions people grow coffee and tea. Malaria is present, like in East Africa one is advised to take a prophylactic drug such as Mephloquin.
There is a large number and variety of languages concentrated in a small territory, e.g. PNG (area the size of Sweden) has some 800 languages. (In East Africa this ratio is probably not so so extreme, but still big.) Sometimes neighboring villages speak languages mutually unintelligible (e.g. the people of Asaro claimed that they don't understand the language spoken 20km away in Goroka). Many people can speak multiple languages (e.g. English, Tok Pisin, and a couple of regional languages). Most of the local newspapers are in English. To us, this makes the local culture and daily events much more accessible, e.g. compared to South America. The basics of the main local language (Tok Pisin in PNG and Kiswahili in most of East Africa) can be easily picked up by reading road signs and advertisements, and overhearing conversations on the street because the languages use the Latin alphabet and have a simple correspondence between spelling and pronunciation. Tok Pisin is simpler, having a large overlap with English in the vocabulary (one local claimed that Tok Pisin has become and is becoming more like English over the years).
There is no "white man" ("muzungu") in sight unless you go in to a fancier hotel, e.g. Bird of Paradise in Goroka or Madang Resort in Madang. The skin color of the locals is almost as dark as in East Africa.
Many people can be seen by the road or on the road, walking long distances to work or to school. Some of them wear basic sandals (but no Masai tire sandals like in East Africa), many are barefoot. Schoolchildren wear bright-colored uniforms. Grown men carry machetes (called "bush knifes" in PNG), schoolchildren carry firewood to bring it to the teacher for the cooking of lunch (not sure if this was the case in East Africa as well). The passing cars and buses have to honk all the time in order to clear the road.
The public transportation is based on 15-seater Toyota Hiace and 25-seater Toyota Coaster buses which are generally referred to as PMV (Public Motor Vehicle). Every bus comes with a driver and a guy who is in charge of announcing the destination, helping with the bags and collecting the fare. The bus leaves only when it's full, circling around the main market place for hours until this happens. These buses travel longer distances, e.g. from Mt. Hagen to Madang it takes some 12h. The PMVs are not overloaded with passengers, respecting a law that requires a dedicated seat for each passenger. For a larger bag one has be pay a full seat price (at least if you are a tourist). PMVs travelling from the Coast to the Highlands are fully packed with sacks of betel nut (which only grows on the Coast). Overall the experience is similar to East Africa with its dala-dalas and matatus, which have no fixed departure times as they wait until the bus gets full (or sufficiently overloaded, in the case of East Africa). (The towns where we stayed where relatively small, so there was no inner-town public transportation system (e.g. taxis, boda-bodas, or rickshaws).)
Roads are full of potholes and sometimes partly washed away. This makes even short distances very long to travel. There are no tunnels through the mountains, e.g. the Goroka-Madang road makes a huge detour and takes 7h to cover (flight would be about 15min).
Roadside ads show the presence of cell phone networks ("Top up here!"), soap companies ("Strongpela bikpela sop!"), Coca-Cola, and AIDS. Everybody seems to have a cell phone, people are constantly calling and texting. SMS banking has recently been introduced. Cell phones are more widespread than electricity, e.g. there are public charging stations where for K2 one can charge his/her phone.
Many Christian churches, but no mosques like in East Africa.
Milo is present.
Locals are very friendly and welcoming. The scariest encounters are with the local ex-pats who tell you stories of crime that they have experienced, e.g. a kiwi gold-miner who carries a "Glock" in his pocket while in Lae or Moresby ("Goroka is safe though"), and a hotel manager whose hotel in Goroka was broken into and a Japanese tourists in there raped and robbed ("Madang is safe though, you see we don't even have razor-wire on the fence around the hotel"). Locals also claim that walking on the streets after sunset is not safe (in Goroka and Madang) when even for a 100m walk from the hotel where you had dinner to the guesthouse where you are staying you should arrange a transport.
There are roadside produce-stands and larger markets in town centers where people sell mostly fruits and vegetables: green oranges, sweet potatoes, peanuts, large green bananas. Oranges are arranged into small conical shapes. Many people just sit around seemingly doing nothing. Garbage is scattered all over the area.
There are roadside vendors who sell peanuts, boiled eggs, cigarettes (one by one) etc. to the passing PMVs. People who want to purchase something try to catch their attention with the psst-sound instead of saying "Excuse me...".
Pairs of men can be often seen holding hands. Is it a sign of friendship like in East Africa?
People (especially women) wear colorful clothing.
Wealthy people have many wives, but this practice seems to be more followed in the villages. To acquire a wife one must pay "bride price" (thus the need for wealth) which is composed of cash, pigs, and cassowaries.
Children like to have their photo taken and are very interested in the outcome.
In front of larger hotels, locals sell their handicraft, e.g. tribal masks carved of wood (or made of clay, in case of the Asaro mudmen masks), paintings, string bags (bilum), etc.
As a tourist, travelling in PNG can be very expensive as the infrastructure (e.g. budget tour operators and hostels) is not fully developed yet, e.g. most hotels cater for the business traveler.
The first curious thing that one notices in PNG is the chewing of betel nut (actually "acre nut"?) or "buai" as it is called in Tok Pisin. You notice that airport departure halls and hotels forbid this practice (similarly to smoking) as there are signs everywhere. But once you're on the street you see chewing and spitting people (both men and women) everywhere (one local claimed that 95% of the people (grownups?) chew). Their bright red gums shine over their black teeth when they smile.
Chewing is known to cause oral cancer but nobody cares. Everywhere there are larger and smaller betel nut markets. The cost of one nut is K0.1 on the coast and K0.5 in the Highlands (where the tree does not grow due to the colder climate). Some people spend K10 per day on chewing, some much more.
Chewing technique: The seed of the betel nut is first removed from the shell cracking the nut open with your teeth, the seed is then chewed into a mass, a mustard seed is then tipped into lime (Calcium hydroxide), the tip is bitten off and chewed together with the nut. The effect of the lime turns the whole mass bright red. Some people swallow the whole thing, but most spit it out after some chewing. Some people chew 4 nuts at one time.
This nut tree also grows in East Africa (according to Wikipedia) but we didn't notice it being used there. The whole practice (especially the use of calcium hydroxide to release the alkaloid stimulants) is thus more similar to the coca leaf chewing in Bolivia and Peru.
Internet in PNG is very expensive, one can easily pay 10 USD per one hour of surfing. In Kenya and Tanzania, one hour usually costs less than a dollar, even in fancier hotels one doesn't pay more than 4 USD.
Women in PNG do not carry buckets and sacks on their heads, but occasionally they attach the bilum-bag on their forehead, hanging down on their backs.
Children in PNG are not as fascinated by "white men" so that they would come running shouting and waving as you walk or drive by.
There are small graveyards within villages. In East Africa we didn't notice any.
People in PNG are not as aggressively offering their products and services as in East Africa. Hardly anybody offers to give you a "good price". Our most Africa-like experience (regarding having to buy a service that you don't need) took place at the Goroka market. We got off the PMV after a 5h trip from Mount Hagen. Before we could ask the locals for the directions to our accommodation, Lutheran Guesthouse, 3 local youths approached us and offered to show us where Lutheran Guesthouse is and even carry our bags there. We didn't let them carry our bags and told them that they don't have to come with us, we would be grateful if they just pointed us to the right direction. They walked with us anyway and later wanted 100 Kina (approx. 30 USD) for their service telling us that we would have been robbed if they hadn't escorted us. We explained to them politely that 100 Kina is a bit outrageous for a 5min service which we didn't need and which involved a workforce unnecessarily large (3 people), and the price of which was not introduced up front. We agreed to tip them 2 Kina, but they didn't want that in the end. We left as friends. They offered to escort us to the airport the next day. We didn't take this offer.
Every man wears a beard. Many women have facial tattoos (simple lines and dots, marking the sign(s) of the boyfriend(s)). Facial tattoos is more a Polynesian feature (found e.g. in Rapa Nui and Tahiti). Some men wear bright shirts with images of the hibiscus flower, just like in Polynesia.
While most buildings in the small villages in East Africa where made of (mud)bricks, in PNG the houses had walls made of reed and thatched roofs. In the coastal regions the buildings where on stilts for better ventilation.
While East Africa is full of all kinds of large and small wild animals, in PNG one can only find the cuscus and the cassowary. There is a large variety of birds (of paradise) though. The main domestic animal in PNG (especially in the Highlands) is the pig, while in East Africa it's more the cow. Similarly in both countries, the number of animals owned shows the wealth and power of the person.
As for sports, the locals seemed to be more into Australian rugby league rather than English soccer league like in East Africa.